Can anyone help I don’t understand how to do this? I could give Brainliest

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

Is of - 4x + 2? a. 3 b. 4 c. 6 d. 5

The half-life of a certain material is 0.004 second. approximately how much of a 20-gram sample will be left after 0.016 second? a. 5 grams b. 16 grams c. 0.32 gram d. 1.25 grams