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