Answer:
See attachment
Explanation:
There are 4 possible phenotypes: purple smooth, white smooth, purple wrinkled and white wrinkled.
We know that purple is dominant to white (P = purple, p = white). So PP = purple, Pp = purple, and pp = white.
We know that smooth is dominant to wrinkled (R = smooth, r = wrinkled). So RR = smooth, Rr = smooth and rr = wrinkled
If you had no idea where to start, you could start drawing up punnet squares with parents of random genotypes. However, the numbers are in a classic Mendelian ratio for a dihybrid cross (with heterozygous parents). That is, the nubmers are 75:28:25:8, which is roughly 9:3:3:1.
The possible genotypes are listed in the punnet square, which would give phenotypes of 9 purple smooth: 3 white smooth: 3: purple wrinkled: 1 white wrinkled
