Question:
Solve 25*f - 69 + 79 = 485 for f..

Answer:
19

Question:
Solve 166*s + 12 = 160*s for s..

Answer:
-2

Question:
Solve 0 = -69*r + 139*r + 560 for r..

Answer:
-8

Question:
Solve 58*f - 47*f - 43*f - 992 = 0 for f..

Answer:
-31