Question:
Solve -75*q = -81*q - 18 for q..

Answer:
-3

Question:
Solve 199*r - 276*r = -231 for r..

Answer:
3

Question:
Solve 4713*v - 4843*v + 2600 = 0 for v..

Answer:
20

Question:
Solve 86*q - 80 = 66*q for q..

Answer:
4