Question: What is the solution?

Solve 3*w = -4*w + 21 for w.

Answer: 3

Question: What is the solution?

Solve -15*z + 6 = 6 for z.

Answer: 0

Question: What is the solution?

Solve 2768 = -13*k - 54*k + 691 for k.

Answer: -31

Question: What is the solution?

Solve 0 = -23*z + 5*z + 54 for z.

Answer:
3