Question: What is the solution?

Solve 8*u = 15 - 31 for u.

Answer: -2

Question: What is the solution?

Solve 6940*a - 51 = 6943*a for a.

Answer: -17

Question: What is the solution?

Solve 17*b = 15*b + 10 for b.

Answer: 5

Question: What is the solution?

Solve -138*o - 951 + 447 = 1545 + 849 for o.

Answer:
-21