Question

How to solve 3x+y=-14;-2x-y=9

Answer 1

This is a set of simultaneous equations.
3x+y=-14
-2x-y=9
Use elimination by addition
x=-5
the substitute for y
y=1

Answer 2

3x+y=-14
-2x-y=9
++++++++++++
x=-5
y=1