Question:
Solve -13*z = 28 - 15 for z..

Answer:
-1

Question:
Solve -8*a + 21 = -15*a for a..

Answer:
-3

Question:
Solve 695*r - 687*r = -8 for r..

Answer:
-1

Question:
Solve 0 = 42*v - 11*v - 12*v + 437 for v..

Answer:
-23