The "solution" to a system of equations basically means an ordered pair that makes both equations true when you put it into the equation. In other words, a value that works! So let's try it.
A is (2, -3). x is 2, y is -3. x+y=-1. 2+(-3)=-1. 2-3=-1. -1=-1. This works! But it needs to work in BOTH equations, so let's try that. x-3y=11. 2-3(-3)=11. 2+(-3*-3)=11. 2+9=11. 11=11! This is TRUE, so A is correct!!
Answer: A (2, -3)