PLZ HELP {systems of elimination}

Hey there! :) 

We are given two equations. 

Equation 1 is : x + y = -3

Equation 2 is : 5x + 7y = -9

In order to solve this, we have to multiply ALL of equation #1 by 5, so that both equations have "5x" in it.

Equation 1: 5(x + y = -3)

Simplify.

5x + 5y = -15

This new equation is now being called equation #3.

So, line up equations #2 and #3.

Equation 2 : 5x + 7y = -9
Equation 3 : 5x + 5y = -15

Notice how the x's, y's, and regular numbers are lined up with one another. Using that, we can subtract equation #3 from #2.

5x - 5x = 0

7y - 5y = 2y

-9 -(-15) = 6

So, we now have this : 

2y = 6

Divide both sides by 2.

2y ÷ 2 = 6 ÷ 2

Simplify.

y = 3

So, now that we have the value of y, very simply plug in 3 for y in equation #1.

Equation 1 : x + y = -3

x + (3) = -3

Subtract 3 from both sides.

x + 3 - 3 = -3 - 3

Simplify.

x = -6

So, our answers are :

x = -6, y = 3

~Hope I helped!~