# How do you solve 5x + 4x + 7 = x + 15?

May 29, 2018

Combine like terms and rearrange to solve for $x$. You will find that $x = 1$

#### Explanation:

First, combine like terms on the Left Hand Side (LHS):

$5 x + 4 x + 7 = x + 15$

$x \left(5 + 4\right) + 7 = x + 15$

$9 x + 7 = x + 15$

Next, we'll subtract 7 from both sides, which effectively moves the 7 to the Right Hand Side (RHS), and we will also subtract $x$ from both sides, moving all $x$-related terms to the LHS:

$9 x \cancel{+ 7} \textcolor{red}{\cancel{- 7}} \textcolor{b l u e}{- x} = \cancel{x} + 15 \textcolor{red}{- 7} \textcolor{b l u e}{\cancel{- x}}$

$9 x \textcolor{b l u e}{- x} = 15 \textcolor{red}{- 7}$

$8 x = 8$

Finally, divide both sides by $x$'s coefficient (8):

$\frac{\cancel{8} x}{\textcolor{red}{\cancel{8}}} = \frac{8}{\textcolor{red}{8}}$

color(green)(x=1

May 29, 2018

$x = 1$

#### Explanation:

$5 x + 4 x + 7 = x + 15$

$5 x + 4 x - x = 15 - 7$

$8 x = 8$

$x = 1$