Question: What is the solution?

Solve -148*r + 68*r = -1840 for r.

Answer: 23

Question: What is the solution?

Solve -76885*w = -76859*w + 52 for w.

Answer: -2

Question: What is the solution?

Solve -21 = 5*u - 12*u for u.

Answer: 3

Question: What is the solution?

Solve 13*u + 5005 + 2720 = 322*u for u.

Answer:
25