question: Teacher asked me this: Solve 20 = 40*s - 36*s for s.
++++++++++
answer: 5

question: Teacher asked me this: Solve -2 + 6 = 2*r for r.
++++++++++
answer: 2

question: Teacher asked me this: Solve -64663*c = -64708*c - 810 for c.
++++++++++
answer: -18

question: Teacher asked me this: Solve 239*l + 220 = 229*l for l.
++++++++++
answer:
-22