The equation for the graph

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)

Yahir designs bracelets. he uses between 9 and 15 red and yellow beads in the ratio of 2 red bead to 5 yellow beads. drag the beads into the container to meet these requirements

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?