Ahhh please hellp

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

Find the number of positive three-digit even integers whose digits are among 9, 8, 7,5, 3, and 1.

The average number of vehicles waiting in line to enter a parking lot can be modeled by the function f left parenthesis x right x squared over 2 left parenthesis 1 minus x right parenthesis endfraction , where x is a number between 0 and 1 known as the traffic intensity. find the rate of change of the number of vehicles waiting with respect to the traffic intensity for the intensities (a) xequals0.3 and (b) xequals0.6.