9 years from now, John will be 3 times as old as he was 11 years ago. How old is he now?
Let J represent John’s age.
We have J + 9 = 3(j − 11)
So, J + 9 = 3J − 33
So, 9 = 2J − 33
So, 42 = 2J
Which means that John’s age is J = 42 / 2 = <<42/2=21>>21
#### 21