Question:
Solve -8*m - 54 = -17*m for m..

Answer:
6

Question:
Solve 17 - 31 = 7*x for x..

Answer:
-2

Question:
Solve 439 - 457 = 6*l for l..

Answer:
-3

Question:
Solve -4*r = -57*r - 31*r - 168 for r..

Answer:
-2