Q: What is the solution?
Solve 0 = -7*o + 8*o - 4 for o.

A: 4

Q: What is the solution?
Solve 0 = -4*w - 6*w + 6*w for w.

A: 0

Q: What is the solution?
Solve 13*d = d + 72 for d.

A:
6