Q: Solve:
Solve 561 - 13 = -33*u + 53 for u.

A: -15

Q: Solve:
Solve -1 = 4*r - 17 for r.

A: 4

Q: Solve:
Solve 1536 = -260*f - 14*f - 448*f - 46*f for f.

A:
-2