It is exponentially each time you are dividing by 4/3
The ages are consecutive even numbers.
The youngest child is (x+3) years old.
Every even number is 2 more than the one before it.
So the three ages are
(x + 3), (x + 5), and (x + 7).
Their sum is x+3 + x+5 + x+7 = 3x + 15
But we're told that their sum is 42, so we can write
3x + 15 = 42 <== the equation
Subtract 15 from each side: 3x = 27
Divide each side by 3 : x = 9 <== the solution
So the three ages are 12, 14, and 16.
The oldest child is 16 years old.
