Could someone help me on this math question !

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

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?

I’m confused on how to work the pie charts