Solve 397*t = -3138 + 756 for t.
Solve this plz.

A: -6

Solve 1633903*s - 1633876*s + 972 = 0 for s.
Solve this plz.

A: -36

Solve -40*a + 405 + 435 = 2*a for a.
Solve this plz.

A:
20