2x-4y=40
2y=-8-5x

simplyfying the 2nd eq:
y=-4-5/2x

substitute back into the 1st eq :
2x - 4(-4 -5/2x) = 40

solve it for x
x = 2 and subst back into the original eq & y=-9

2x-4y=40
2y=-8-5x

2x-4y=40
5x+2y=-8

2x-4y=40
10x+4y = -16

eliminate the y's

12x =24
x = 2

2x-4y=40
4 - 4y = 40
-4y = 40 - 4
-4y = 36
y = -9