Help for this question, please and thanks

What is the best reason for jacinta to have a savings account in addition to a checking account

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

Kayla wants to find the width, ab, of a river. she walks along the edge of the river 65 ft and marks point c. then she walks 25 ft further and marks point d. she turns 90° and walks until her location, point a, and point c are collinear. she marks point e at this location, as shown. (a) can kayla conclude that δ and δ are similar? why or why not? (b) suppose de = 15 ft. what can kayla conclude about the width of the river?