Question:
Solve x = -x for x..

Answer:
0

Question:
Solve -10*s = -31 + 21 for s..

Answer:
1

Question:
Solve -88*y + 153 = 79*y - 138*y + 1371 for y..

Answer:
-42

Question:
Solve 620*k - 223*k + 5848 = 311*k for k..

Answer:
-68