Solve -17*s = -18*s - 4 for s.
Solve this plz.

A: -4

Solve 0 = -27*f + 126 - 315 for f.
Solve this plz.

A: -7

Solve -15895*r + 160661 = -584910 - 420490 - 423439 for r.
Solve this plz.

A:
100