It said that dogs age seven years for every “people year.” Mason’s dog, Shep, was born on Mason’s eighth birthday. When Mason was nine years old, Shep was seven years old. If Shep is fifty-six years old, how old is Mason?

well, 56 = 7*8, so ...

56 = 7x8 or 8x 7

To find out how old Mason is, we can determine the number of "dog years" that have passed since Shep was born and then convert those years into "people years".

If Shep ages seven years for every "people year", then Mason's ninth birthday marks the completion of one "people year" since Shep was born. At this point, Shep would be seven years old in "people years".

So, to calculate the number of "dog years" that have passed since Shep was born, we subtract 7 (Shep's age at Mason's ninth birthday) from 56 (Shep's current age in "dog years"): 56 - 7 = 49 "dog years".

Since each "dog year" is equivalent to seven "people years", we can find out how old Mason is by multiplying the number of "dog years" by seven: 49 * 7 = 343 "people years".

Therefore, Mason is 343 years old.