Question

Shawn is 23 years old, and Yu Yan is 15 years old. How many years ago was Shawn 3 times as old as Yu Yan was?

Answer 1

11

Explanation:

Now:

Shawn: 23

Yu Yan: 15

x years ago:

Shawn: 23 - x

Yu Yan: 15 - x

x years ago, Shawn was 3 times as old as Yu Yan.

23 - x = 3(15 - x)

23 - x = 45 - 3x

2x = 22

x = 11

Check:

11 years ago Shaw was 23 - 11 = 12, and Yu Yan was 15 - 11 = 4.

12 is indded 3 times 4.

Answer: 11