Answer: Johnathon could walk 84 blocks in 3 minutes.
Explanation:
So you already know that he can walk 7 blocks in 15 seconds. There are 60 seconds in a minute. So you would multiply 15 by 4 to get 60 which means you would also multiply 7 by 4. Which is 28. Then you would multiply it by 3 since there are 3 minutes. 28 times 3 is 84.