Answer:
See the answer below
Explanation:
Genotype of a true-breeding white, disk-shaped fruit = WWDD
Genotype of a true-breeding yellow, sphere-shaped fruit = wwdd
Crossing the two:
  WWDD   x   wwdd
       WwDd
All the offspring (100%) will have the genotype WwDd with white, disk-shaped phenotype.
Assuming the cross is advanced to F2:
 WwDd   x   WwDd
W_D_ Â Â 9 Â White, disk-shaped (9/16)
W_dd   3  White, sphere-shaped (3/16)
wwD_ Â Â 3 Â Yellow, disk-shaped (3/16)
wwdd    1   Yellow, sphere-shaped (1/16)
(See the attached image for the Punnet's square)