To solve a linear equation with variables on both sides, we bring all variables to one side of the equation and all constants to the other side.

For example, let's solve the following equation:

5x = 2x + 12

Notice that we have 5x on the left-hand side and 2x on the right-hand side. Since the variable on the left-hand side has a larger coefficient, let's bring all the variables to this side.

The first step is to remove the \color{blue}2x from the right-hand side. We can do this by subtracting it from both sides of the equation, as follows:

\begin{align*} 5x &= 2x + 12 \\[5pt] 5x - {\color{blue}{2x}}&= 2x + 12 - {\color{blue}{2x}} \\[5pt] 3x &= 12 \end{align*}

Finally, we divide both sides of the equation by 3\mathbin{:}

\begin{align*} \require{cancel} 3x &= 12 \\[5pt] \dfrac{3x}{3} &= \dfrac{12}{3} \\[5pt] \dfrac{\cancel{3}x}{\cancel{3}} &=4\\[5pt] x &=4 \end{align*}

So x=4 is our answer, and we're done.

We can check that x=4 is correct by substituting back into the original equation:

\begin{align*} 5x &\stackrel{?}{=} 2x + 12 \\[5pt] 5(4) &\stackrel{?}{=} 2(4) + 12 \\[8pt] 20 &= 20 \qquad{\color{green}{\checkmark}} \end{align*}

FLAG

Given that 12 - 5m = 3m , what is the value of m?

EXPLANATION

We must bring all variables to one side of the equation and all constants to the other side.

Notice that we have -5m on the left-hand side and 3m on the right-hand side. Since the variable on the right-hand side has a larger coefficient, let's bring all the variables to this side.

The first step is to remove the -5m from the left-hand side. We do this by adding {\color{blue}5m} to both sides:

\begin{align*} 12 - 5m &= 3m \\[5pt] 12 - 5m + {\color{blue}5m} &= 3m+ {\color{blue}5m}\\[5pt] 12 &= 8m \end{align*}

Finally, we divide both sides of the equation by 8\mathbin{:}

\begin{align*} \require{cancel} 12 &= 8m \\[5pt] \dfrac{12}{8} &= \dfrac {8m}{8} \\[5pt] \dfrac{3}{2} &= \dfrac {\cancel {8}m}{\cancel 8} \\[5pt] \dfrac{3}{2} &= m\\[5pt] m &=\dfrac{3}{2} \end{align*}

FLAG

Solve for $z$ where $3z = z + 8.$

a
$z=4$
b
$z= 3$
c
$ z=-1$
d
$z= -2$
e
$z=2$

Given that $p + 12 = 5p$, what is the value of $p?$

a
$-2$
b
$2$
c
$-1$
d
$3$
e
$-3$

What is the solution to the equation $28−2y = 5y?$

a
$y=4$
b
$y=-5$
c
$y=6$
d
$y=-3$
e
$y=\dfrac {28} 3$

Let's now solve the following equation:

9x -9= 1+4x

To solve this equation, we must bring all variables to one side of the equation and all constants to the other side.

Notice that we have 9x on the left-hand side and 4x on the right-hand side. Since the variable on the left-hand side has a larger coefficient, let's bring all the variables to this side.

The first step is to remove the 4x from the right-hand side of the equation. We do this by subtracting {\color{blue}4x} from both sides:

\begin{align*} 9x -9 &= 1+ 4x \\[5pt] 9x- 9 - {\color{blue}4x} &= 1 + 4x -{\color{blue}4x} \\[5pt] 5x - 9 &= 1 \end{align*}

Next, we remove the -9 from the left-hand side. We do this by adding {\color{red}9} to both sides:

\begin{align} \require{cancel} 5x -9 &= 1\\[5pt] 5x -9 + {\color{red}9} &= 1 + {\color{red}9}\\[5pt] 5x & = 10\\[5pt] \end{align}

Finally, we divide both sides of the equation by 5\mathbin{:}

\begin{align} 5x & = 10\\[5pt] \dfrac{5x}{5} & = \dfrac{10}{5}\\[5pt] \dfrac{\cancel{5}x}{\cancel{5}} & = 2\\[5pt] x& = 2 \end{align}

So x=2 is our answer. We can check that this is correct by substituting back into the original equation:

\begin{align*} 9x - 9 &= 1+4x \\[5pt] 9(2) - 9 &\stackrel{?}{=} 1+4(2) \\[8pt] 18 - 9 &\stackrel{?}{=} 9 \\[8pt] 9 &= 9 \qquad{\color{green}{\checkmark}} \end{align*}

FLAG

Solve the equation 3x-12 = 5x + 8.

EXPLANATION

We must bring all variables to one side of the equation and all constants to the other side.

Notice that we have 3x on the left-hand side and 5x on the right-hand side. Since the variable on the right-hand side has a larger coefficient, let's bring all the variables to this side.

The first step is to remove the 3x from the left-hand side of the equation. We do this by subtracting {\color{blue}3x} from both sides:

\begin{align*} 3x-12 &= 5x + 8 \\[5pt] 3x-12 - {\color{blue}3x} &= 5x + 8 - {\color{blue}3x}\\[5pt] -12 &= 2x + 8 \end{align*}

Next, we remove the 8 from the right-hand side. We do this by subtracting {\color{red}8} from both sides:

\begin{align*} \require{cancel} -12 &= 2x + 8 \\[5pt] -12 - {\color{red}8}&= 2x + 8 - {\color{red}8} \\[5pt] -20 &= 2x \end{align*}

Finally, we divide both sides of the equation by 2\mathbin{:}

\begin{align*} - 20 &= 2x \\[5pt] \dfrac{-20}{2} &= \dfrac{2x}{2} \\[5pt] -10 &= \dfrac{\cancel{2}x}{\cancel{2}} \\[5pt] -10 &=x \\[5pt] x &= -10 \end{align*}

FLAG

What is the solution to the equation $5t-1=5+2t?$

a
$t = 5$
b
$t=3$
c
$t = 7$
d
$t = 4$
e
$t=2$

Solve for $p$ where $2p + 1 = 4 - 4p.$

a
$p = \dfrac{1}{2}$
b
$p = -2$
c
$p = -\dfrac{3}{2}$
d
$p = 2$
e
$p = \dfrac{1}{3}$

Solve for $k$ where $2-k=3k+9.$

a
$k=-2$
b
$k=-\dfrac{7}{4}$
c
$k=-\dfrac{7}{2}$
d
$k=2$
e
$k=\dfrac{7}{4}$

Solve for t where 2(t+3)= 5t-3.

EXPLANATION

First, we expand the parentheses on the left-hand-side:

\begin{align} 2(t+3) &= 5t -3\\[5pt] 2 \cdot t + 2 \cdot 3 &= 5t-3 \\[5pt] 2t + 6 &= 5t-3 \end{align}

Now, we must now bring all variables to one side of the equation and all constants to the other side.

Notice that we have 2t on the left-hand side and 5t on the right-hand side. Since the variable on the right-hand side has a larger coefficient, let's bring all the variables to this side.

The first step is to remove the 2t from the left-hand side of the equation. We do this by subtracting {\color{blue}2t} from both sides:

\begin{align*} 2t + 6 &= 5t-3 \\[5pt] 2t + 6 - {\color{blue}2t} &= 5t -3 - {\color{blue}2t}\\[5pt] 6&= 3t - 3 \\[5pt] \end{align*}

Next, we remove the -3 from the right-hand side. We do this by adding {\color{red}3} to both sides:

\begin{align*} 6 &= 3t - 3 \\[5pt] 6 + {\color{red}3} &= 3t - 3+{\color{red}3} \\[5pt] 9 &= 3t \\[5pt] \end{align*} Finally, we divide both sides of the equation by 3\mathbin{:}

\begin{align*} \require{cancel} 9 &= 3t \\[5pt] \dfrac{9}{3} &= \dfrac{3t}{3} \\[5pt] 3 &= \dfrac{\cancel{3}t}{\cancel{3}} \\[5pt] 3 &= t \\[5pt] t&= 3 \end{align*}

FLAG

If $3(a - 2) = a$, then $a=$

a
$3$
b
$1$
c
$8$
d
$7$
e
$5$

Solve for $p$ where $2(2p + 1) = - p.$

a
$p = \dfrac{1}{3}$
b
$p =\dfrac{3}{7}$
c
$p = -\dfrac{2}{5}$
d
$p = -\dfrac{5}{4}$
e
$p =\dfrac{6}{11}$

If $5(x-3) = 3(x + 7) + 5x,$ then $x =$

a
$-12$
b
$-\dfrac{3}{2}$
c
$-6$
d
$\dfrac{7}{2}$
e
$\dfrac{11}{2}$
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