Question:
Solve -4*n = -7*n - 15 for n..

Answer:
-5

Question:
Solve -1686*q + 29330 = -2524*q for q..

Answer:
-35

Question:
Solve -8*r = -2*r - 0*r + 59*r for r..

Answer:
0

Question:
Solve 1648*f - 1678*f + 294 - 1404 = 0 for f..

Answer:
-37