Q: Solve:
Solve 15*r + 750 = 56*r + 209*r for r.

A: 3

Q: Solve:
Solve 23*a - 66*a - 59*a = 714 for a.

A: -7

Q: Solve:
Solve 0 = -9*s + 105 - 6 for s.

A:
11