# How do you solve the system of equations #-x-2y=9# and #3x+2y=-3# by adding or subtracting?

##### 1 Answer

Jan 27, 2018

See the steps below

#### Explanation:

The first thing you want to do is multiply one equation through by a constant value that will cause one of the variables to have the same coefficient (the value to the left of the variable), but with opposite sign. I will use the

Multiply the first equation by 3 (every term)

Next, add the two equations, which means add like terms

+

Gives us

Notice how the

Now, pick either of the original equations and substitute in

You will find that