Question:
Solve 40 = -25*r + 15*r for r..

Answer:
-4

Question:
Solve -7*i + 88*i - 405 = 0 for i..

Answer:
5

Question:
Solve 0 = 78*i - 85*i + 3 + 18 for i..

Answer:
3

Question:
Solve -q - 55*q - 168 = 0 for q..

Answer:
-3