Answer: 10x - 5y = 40
Reason:
Why 5x - 10y = -12 is wrong (working):
5x - 10y = -12
-10y = -5x - 12
y = 0.5x + 1.2
(positive slope but not the correct y-intercept)
Why 10x - 5y = 40 is correct (working):
10x - 5y = 40
-5y = 40 - 10x
y = 2x - 8
(positive slope and correct y-intercept)
Why 5x + y = 50 is wrong (working):
5x + y = 50
y = -5x + 50
(negative slope and not the correct y-intercept)
Why x - 2y = 10 is wrong (working):
x - 2y = 10
-2y = -x + 10
y = 0.5x - 5
(positive slope but not the correct y-intercept)
Therefore, 10x - 5y = 40 is the answer
