Eight times a number added to "-4," subtracted from twice the sum of three times the number and 8

Amuffin recipe, which yields 12 muffins, calls for cup of milk for every 1 cups of flour. the same recipe calls for cup of coconut for every cup of chopped apple. to yield a batch of 30 muffins, how much flour will be needed in the mix?

What is the rate of change of a line that passes through (2,-5) and (6,-2)?

Ineed to know the answer to this algebra question.