Answer: 9 - 2 yr olds, 18 - 3 yr olds, and 18 - 4 yr olds
Step-by-step explanation:
2 yr olds: [tex]\dfrac{1}{2}x[/tex]
3 yr olds: x
4 yr olds: x
2 yr olds + 3 yr olds + 4 yr olds = Total students
[tex]\dfrac{1}{2}x[/tex] + x + x = 45
[tex]2\dfrac{1}{2}x = 45\\\\\dfrac{5}{2}x = 45\\\\5x = 90\\\\x = 18[/tex]