The four smith children were born at two year intervals. The sum of their ages is 36

6, 8, 10 and 12 years

Step-by-step explanation:

I guess you need to find their ages. This can be done by solving an algebraic equation as follows:

Let x years be the age of the youngest child. Then the ages of the other 3 are x+2, x+4 and x+6 years because they were born at 2 year intervals. So we have the equation:

x + x + 2 + x + 4 + x + 6 = 36

4x + 12 = 36

4x = 24

x = 6

so their ages are 6, 8, 10 and 12 years