Solve by elimination:

-9x-4y=-20

5x+4y=4

Eliminate the y by making them zero.

-9x=-20

5x=4

Combine

-4x=-16

Divide each side by 4 to put the x alone

-4x/4 = - 16/-4

X=4

Plug x=4 back into one of the equations. It does not matter

5 (4) + 4y=4

20+4y=4

-20 - 20

4y=-16

Divide by 4

Y=-4