Mike’s age right now is exactly 3 times his age 3 years hence minus 3 times his age 3 years ago. How old is Mike right now?

Let *m* stand for Mike’s age. Then his age 3 years hence is *m* + 3, and his age 3 years ago is *m* – 3.

So: *m* = 3(*m* + 3) – 3(*m* – 3) = 3*m* + 9 – (3*m* – 9) = 3*m* + 9 – 3*m* + 9 = 18.

Check: If Mike is 18, then in 3 years he’ll be 21, and 3 years ago he was 15. So, does 18 equal 3 x 21 – 3 x 15 = 63 – 45 = 18? Yep.