Forty-five children attend a preschool. The number of two-year-olds is one

half the number of three-year-olds. The number of four-year-olds is the

same as the number of 3-year-olds.

AHow many two-year-olds attend the preschool?
BHow many three-year-olds attend the preschool?
CHow many four-year-olds attend the preschool?