# Question 3317c

May 16, 2017

$x = - 19$

#### Explanation:

When you look at the question it probably looks strange, because when some number ($x$) is ADDED to $39$, the answer gets LESS!

You might be asking how this is possible?

This is a clue that $x$ is a negative number.

Adding a negative number is the same as subtracting a positive, which you are more used to doing.

To solve the equation:

We want to get $\textcolor{red}{x}$ by itself on the left side of the equation.

In an equation, you can do ANY operation you like, as long as you do the same on both sides, to keep the equation in balance.
We need to get rid of the $39$, so color(blue)("subtract " 39# from both sides.

$39 + \textcolor{red}{x} = 20$

$39 \textcolor{b l u e}{- 39} + \textcolor{red}{x} = 20 \textcolor{b l u e}{- 39} \text{ } \leftarrow \left(39 - 39 = 0\right)$

$\textcolor{red}{x} = 20 - 39$

$\textcolor{red}{x} = - 19$

Check using $- 19$ in the place of $\textcolor{red}{x}$

$39 + \left(\textcolor{red}{- 19}\right) = 20$

This is the same as:

$39 - 19 = 20$