Please help me with these thanks!! :)

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.

Simplify the expression. -2/5(10+15m-20n)

When is g(x) = 0 for the function g(x) = 5.23x + 4?