You need to create Punnet square. Since there are four gene sequence from each parent, there are 24 =16 alternatives.
List the various combinations in which the alleles can sort. For the first parent, each p allele can sort with each t allele, so the combinations which involve the P allele are P T1 and P T2 (where the T allele on one chromosome is denoted T1 and the T allele on the other is denoted T2).
The combinations which involve the other p allele are p T1 and pT2. For the second parent, p1 denotes the p allele on one chromosome and p2 denotes the p allele on the second. The possible combinations are p1 T, p1 t, p2 T and p2 t. You line these up on the sides of the grid, do the cross, and look at the frequency at which the different genotypes (and phenotypes) arise to analyze the cross
.If you do a Punnett square based on the gametes of this cross -PT and pT for the first parent and pT and pt for the second parent- the phenotype for this cross would be 2 Purple tall : 2 White tall which means the offsprings would be 50% purple tall and 50% white tall. Two of the offsprings in this cross will have the parental genotypes ,one will be heterozygous for both traits(PpTt) and the fourth offspring will have the genotype ppTT. and so... it is Tt n Pp..