question: Teacher asked me this: Solve 213 - 309 = 102*o - 3870 for o.
++++++++++
answer: 37

question: Teacher asked me this: Solve 0 = -53*f + 828 - 298 for f.
++++++++++
answer: 10

question: Teacher asked me this: Solve 84*u - 65*u = -55*u for u.
++++++++++
answer: 0

question: Teacher asked me this: Solve -189 = -30*b + 5*b + 4*b for b.
++++++++++
answer:
9