let Max's age =m
Kirk's age=k
k=7+4m
k-4m=7.........(i)
k+m=52.........(II)
k=7+4m.........(III)
from equation 1 substitute 7+4m for k in
equation 2.
7+4m+m=52
5m=52-7
5m=45
m=45/5
m=9
.:Max's age is 9 years.
From equation (2) k+m=52
k+9=52
k=52-9
k=43
:. kirk's age is 43 years.