question: Teacher asked me this: Solve 9*f = 21*f for f.
++++++++++
answer: 0

question: Teacher asked me this: Solve -3*z + 6*z + 4 = -z for z.
++++++++++
answer: -1

question: Teacher asked me this: Solve 12 = -7*l - 9 for l.
++++++++++
answer: -3

question: Teacher asked me this: Solve 5787*i + 6650 = 5717*i for i.
++++++++++
answer:
-95