For every 1 year a human ages, a dog ages 7 years.  When Max is 3, how much older, in dog years, will his 3-year-old dog be?
How old will the 3-year-old dog be? ** The 3-year-old dog ages 7 years to one human year so he will technically be 3*7 = <<3*7=21>>21 years old in dog years
How old will Max's 3-year-old dog be? ** Max's dog will be 21 when Max turns 3 so the age difference is 21-3 = <<21-3=18>>18
#### 18