The variable S is used to exemplify Sawyers age. Therefore S-6= Sister’s age. 3(S-6) is used to demonstrate that Sawyer is three times as old as his sister. When broken down it is equal to S=3S-18 where you will add 18 to both sides giving you S+18=3S. Then, you will subtract S from both sides giving you 2S=18 making your final answer 9. Sawyer is 9 years old now.