Answer:
Both parents were heterozygous
Step-by-step explanation:
Lets suppose N is the dominant and n is the recessive.
If both parents are heterozygous, they can create flies with vestigial and normal wings. The result of that is 25% NN, 50% Nn, and 25% nn. If you add up the flies that were vestigial and the flies that were normal, it would be 120. The male and female flies with vestigial wings add up to be 33, 33/120 is 27.5% which is a little over 25%.