If two functions are inverses of each other, then their composition is

Find an equation for the linear function which has slope -10 and x-intercept -7

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.