Formula of area of a semicircle

With #! i’ve tried to figure it out but i can’t.

Omar is going on a road trip! the car rental company offers him two types of cars. each car has a fixed price, but he also needs to consider the cost of fuel. the first car costs $90 to rent, and because of its fuel consumption rate, there's an additional cost of s0.50 per kilometer driven.

Describe the relationship between the angles of similar triangles and the sides of similar triangles