What do you have to add to -2 1/2 to have a result of 2 1/2

For how answer my question this will be the last question can you answer in math subject

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.

Your food costs are $5,500. your total food sales are $11,000. what percent of your food sales do the food costs represent?