How do you solve #2x-y=-1# and #x+y=-5#?
There are several ways to solve a system, so it's always best to choose the simplest method to avoid what we call "nuking mosquitos", i.e. using a complex solution for a simple problem
In this case, I think the easiest way is to sum the two equations: adding the left and right sides, we have
This should make clear why I chose to sum the two equations: we cancel
Once we know the value of