Question:
Solve -154*z + 71*z = -64*z + 209 for z..

Answer:
-11

Question:
Solve -97*v = 100*v + 3940 for v..

Answer:
-20

Question:
Solve -3*w - 10 = -5*w for w..

Answer:
5

Question:
Solve -15*y + 10 = -20*y for y..

Answer:
-2