Q: Solve:
Solve 21*c = 23*c - 4 for c.

A: 2

Q: Solve:
Solve -10 = 150*l - 155*l for l.

A: 2

Q: Solve:
Solve 648*h + 679*h = -639*h + 2054*h - 9856 for h.

A:
112