_2.) If y varies directly as the square of x, and y = 24 when x = 4, find the constant of variation k.

3.) if c varies inversely as d, and c = 30 when d = 9, find d when c = 540.

4.) If x varies jointly as y and z, find the constant of variation if x = 5, z = 8, and y = 480. _

5.) if p varies directly as q and inversely as r, and p = 4 when q = 2 and r = 6, find p when 9 = 4 and r = 8,​