Q: Solve:
Solve 0 = -3*p + 18 - 6 for p.

A: 4

Q: Solve:
Solve 0 = -2*o + 9*o + 21 for o.

A: -3

Q: Solve:
Solve 0 = 351*r + 100*r + 17656 - 969 for r.

A:
-37