Answer: Solution x=27, y-7.2
(1) 2x + 5y= 18
(2) 4x + 20y= -36
Multiply equation (1) by -2:
(1) -4x - 10y= -36
(2) 4x + 20y= -36
Add (1) to (2):
(2) 4x + 20y -4x - 10y = -36 -36
-> 10y = -72
-> y=-7.2
Use the value for y in equation (1) to get x:
(1) 2x + 5(-7.2) = 18
2x -36 = 18
2x = 54
x = 27
Solution (x,y)=(27,-7.2)
