Question:
Solve 0 = -364*s + 391*s + 216 for s..

Answer:
-8

Question:
Solve 6*f - 3 = 9 for f..

Answer:
2

Question:
Solve -16 - 12 = -1443*x + 1450*x for x..

Answer:
-4

Question:
Solve 0 = 33*f - 14 + 113 for f..

Answer:
-3