Idon't understand how to do this. can someone ?

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

What is the radical expression that is equivalent to the expression 27 1 over 5?

Aroulette wheel has 38 slots in which the ball can land. two of the slots are green, 18 are red, and 18 are black. the ball is equally likely to land in any slot. the roulette wheel is going to be spun twice, and the outcomes of the two spins are independent. the probability that it lands one time on red and another time on black in any order is(a) 0.5 (b) 0.25 (c) 0.4488 (d) 0.2244