Solve -20*a + 10 + 50 = 0 for a.
Solve this plz.

A: 3

Solve 1850 - 750 + 790 = -126*d for d.
Solve this plz.

A: -15

Solve 9*c - 16 = 5*c for c.
Solve this plz.

A:
4