Question:
Solve -21 = 9*b - 12 for b..

Answer:
-1

Question:
Solve 20*n - 24 = 24*n for n..

Answer:
-6

Question:
Solve 967*l - 1351*l = 10752 for l..

Answer:
-28

Question:
Solve -4493*m - 168 = -4469*m for m..

Answer:
-7