Apple trees cost $ 30 each, and cherry trees cost $ 40 each. rohan has $ 600 to spend on fruit trees.
a) let x represent the number of apple trees purchased, and let y represent the number of cherry trees purchased.
b) write an equation that illustrates the different ways rohan can purchase apple trees and cherry trees and spend exactly $ 600 .
equation:

Your vet has placed your pet on a diet. the diet is to contain at least 12 mg of fat and at least 14 mg of protein per serving. these requirements are to be obtained from two food sources. source a contains 2 mg of fat and 2 mg of protein per serving. source b contains 1 mg of fat and 3 mg of protein per serving. if source a sells for $1.28 per serving and source b sells for $1.12 per serving, how many servings of each type should be purchased to satisfy the requirements at minimal cost?