Step-by-step explanation:
Let us consider a cross between two plants heterozygous for purple flowers.
Heterozygous Purple (Pp) X Heterozygous Purple (Pp)
Each plant will produce two types of gametes, i.e. 50% gametes carrying (P) allele and 50 % carrying (p) allele.
Checking the probability of fusion between the gametes produced by two plants crossed using Punnet Square method, it is seen that 75% plants will have at least one dominant allele (P) and thus will bear purple flowers. Only 25% plants will have recessive allele in homozygous state (pp). These plants will bear white flowers.
Out of 75% plants bearing purple flowers, 25% will be homozygous Purple (PP) and 50% will be heterozygous purple (Pp)