Two integers, a and b, have a product of -20. what is the greatest possible sum of a and b

Ineed in figuring out this problem.

Acomputer store bought a program at a cost of $10 and sold it for $13. find the percent markup

The total ticket sales for a high school basketball game were $2,260. the ticket price for students were $2.25 less than the adult ticket price. the number of adult tickets sold was 230, and the number of student tickets sold was 180. what was the price of an adult ticket?