Question: What is the solution?

Solve -2*r = -9 + 11 for r.

Answer: -1

Question: What is the solution?

Solve -504*o = 319 - 4855 for o.

Answer: 9

Question: What is the solution?

Solve -12*f - 12*f + 105 = -9*f for f.

Answer: 7

Question: What is the solution?

Solve -49*t - 26*t + 223*t + 11430 = 21*t for t.

Answer:
-90