Solve -123 - 399 = 87*u for u.
Solve this plz.

A: -6

Solve 800 = 19*f + 325 for f.
Solve this plz.

A: 25

Solve 0 = -507*p - 9145 + 4431 - 6947 for p.
Solve this plz.

A:
-23