13. Solve each variation problem. a) If y varies directly as >, and y = 9 when x = 2, what is y when x = -3? b) If P is inversely proportional to w, and P = CO/ N when w = +, what is P when w = 6 c) If J is jointly proportional to G and V, and J = V3 when G = V2 and V = V8, what is J when G = V6 and V = 8? d) If y is directly proportional to u and inversely proportional to the square of v, and y = 7 when u = 9 and v = 6, what is y when u = 4 and V = 8