3times the difference of a number and 7 is 18

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?

Jose bought 20 shares of netflix at the close price of $117.98. in a few years, jose sells all of his shares at $128.34. how much money did jose make? a.) $192.50 b.) $207.20 c.) $212.50 d.) $224.60

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?