How to find intercepts on a piece-wise defined function?

The area of a rectangle is 54x^9y^8 square yards. if the length of the rectangle is 6x^3y^4 yards, which expression represents the width of the rectangle in yards

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

How long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way