Question

SOLVE EACH SYSTEM BY SUBTRACTION
-3x-15y=-39
x+5y=13

Answer 1

Do you understand the principle behind the subtraction method?

Answer 2

yes my math teacher helped me a bit but im still stuck

Answer 3

We use this method in order to eliminate one of the variable from an equation so we could obtain a single variable equation that we could solve.
e.g. x+y=1 is a 2 variable equation whereas x+1=3 is a single variable equation.

So basically we need to either take x or y out. To do so, in both equations, we MUST have the same coefficient attached to the same variable. In this case, we can easily subtract the two equations and get rid of the x variable.