Q: Solve:
Solve -8*s - 12*s + 90 = -30*s for s.

A: -9

Q: Solve:
Solve 78*f - 42*f = 73*f - 666 for f.

A: 18

Q: Solve:
Solve 16*t - 19*t - 5 = 1 for t.

A:
-2