How do you use addition to solve for a system of linear equations?

3x + 7y = -2
2x + 3y = -3
___________
5x +10y = -5

use that to solve

Those questions seem kind of out of the ordinary, I think all you have to do is the following.

3x+7y+2=0
-7y=3x+2
y=-3/7x-2/7

2x+3y=-3
2x+3y+3=0
-3y=2x+3
y=-2/3x-1

I just manipulated them into standard form, I don't know what you're supposed to solve for. Hope I helped.

To solve a system of equations using addtion, you will have to multiply each one by a different number to make one variable the same, but with different signs.
Take the first one times 2 to get : 6x + 14y = -4
Take the second one times -3 to get : -6x - 9y = 9

We now have x with 6 and - 6

Now if you add these, the  x's will drop out, and you will end up with : 5y = 5
So y = 1
Plug this into either equation to find x
2x + 3(1) = -3
2x + 3 = -3
2x = -6
x = -3

To check : 3(-3) + 7(1) =? -2
-9 + 7 = -2  CHECK
2(-3) + 3(1) =? -3
-6 + 3 = -3 CHECK