Add -2 (second equation) to the first equation to eliminate x :
(2x - 4y) + (-2) (x + 5y) = 10 + (-2) • 40
(2x - 4y) + (-2x - 10y) = 10 - 80
-14y = -70
y = 5
Plug this into either equation (I'll use the second) to solve for x :
x + 5y = 40
x + 5 • 5 = 40
x + 25 = 40
x = 15
