(picture included) can someone me with 4?

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.

The center of the circumscribed circle lies on line segment and the longest side of the triangle is equal to the of the circle.

David pays a 20% income tax on his $2,100 salary. how many dollars is the tax? show work