15 feet out of 36 feet how do you write a ratio as a fraction in simplest form

Ms. ortiz sells tomatoes wholesale. the function p(x)=-80x^2+320x-10, graphed below, indicates how much profit she makes on a load of tomatoes if she makes on a load of tomatoes if she sells them for 4-x dollars per kilogram. what should ms. ortiz charge per kilogram of tomatoes to make on a load of tomatoes?