How many moles of carbon are in 5.2 moles of C7H18?

There is a shortcut to this Chem question. simply look at this problem as if it were a cooking recipe. you have 7 parts Carbon and 18 Parts Hydrogen for a total of 25 parts. Simply divide 5.2 by 25 then multiply by 7 to get your answer.

(5.2 / 25) 7 = 1.456 moles