Answer:
9 two year olds, 18 three year olds, 18 four year olds
Step-by-step explanation:
Let's say x is the number of 2 year olds. There are double the number of three year olds (2x) . Four year olds is the same as 3 year olds (2x).
x + 2x +2x = 45
5x=45
x= 9
Double is 18 for 3 and four year olds.