I need big help, what are the step by step math problem and the answer to (18/-2)^2?

Solve - pv + 40 < 65 for v solve 7w - 3r = 15 for r

Aclass consists of 55% boys and 45% girls. it is observed that 25% of the class are boys and scored an a on the test, and 35% of the class are girls and scored an a on the test. if a student is chosen at random and is found to be a girl, the probability that the student scored an ais

If the tip varies directly with the number of guest which equation represents between the tip, t, and the number of guest, g?