A dihybrid cross tracks 2 genetic traits from 2 parents.
First you need to look at all the potential combinations of each parent
Parent 1: heterozygous tall & heterozygous round Tt & Rr
Parent 2: Homozygous dominant tall & wrinkled TT & rr
(use something like foil and look at all the possible options)
Parent 1: TR , tR, Tr, or tr
Parent 2: Tr
TR . tR . Tr tr
Tr . TT Rr . Tt Rr . TT rr Tt rr
Results show that 50% of offspring will be Tall & Round and 50% will be tall and wrinkled (phenotype)
however genotype displays a 1:1:1:1 ratio as none of the genotypes are exactly the same