multiple question I need to knowthe stepsto getting to the answers;

Given f(x) = -8 and g(x) = 5x+9, find the Product, if fg)(x)

which way do I go from here???

Then theseequationsof direct and inversevariations:

Find an equation of variation if y varies directly as x and y = 0.1 when x = 0.5

Find an equation of variation if y varies inversely as x and y = 9, when x = 20

Find an equation of variation if y varies Directly as x and inversely as z, and y = 18 when 2 and z = 4.