We need to develop an equation with only one variable in it so that we may begin to work out each age.
Let x be the age of Julie, such that Jake = x + 4
x + (x + 4) = 22 (sum of their ages)
2x + 4 = 22
2x = 18
x = 9
So, Julie is 9 years old and Jake is 13 years old.
