Multiply first equation by 2:
8x-2y=18
5x+2y=8
Add the equations:
13x=26, x=26/13=2.
Substitute this value for x in either equation. Use 4x-y=9:
4×2-y=9, 8-y=9, y=8-9=-1. If we use 5x+2y=8:
5×2+2y=8, 10+2y=8, 2y=8-10=-2, y=-2/2=-1, we get the same result.
SOLUTION x=2, y=-1.