The ratio of the ages of three children is 2:4:5
Total ratio of their ages is

And the sum of their ages is 33
Using individual ratios to find the ages of the children
For the child with the ratio of 2, the age is

The child with the ratio of 2 is 6 years old
For the child with the ratio of 4, the age is

The child with the ratio of 4 is 12 years old
For the child with the ratio of 5, the age is

The child with the ratio of 5 is 15 years old
Hence, the age of each children is 6, 12 and 15 years