Question

Solve the system of equations:
x + y = 5
x – y = -9

Answer 1

2x=-4
x=-2
-2+y=5
y=7

Answer 2

add the equations x+y+x-y=5-9 => 2x=-4 -> x=-2.
putting value of x in equation 1
-2+y=5
y=7;