I’m not sure how to do angle relationships so does anyone know how to find x?

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

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate. in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible