Answer:
100%
Explanation:
Assuming the gene for polydactyly is represented by P. Normal finger will be represented by p.
A woman that is homozygous for polydactyly trait will have genotype PP while a man with normal 5 fingers and toes will have the genotype pp (since P is dominant over p).
PP  x  pp = Pp, Pp, Pp and Pp.
All the offspring will have the genotype Pp and since P is dominant over p, it means all the offspring will have polydactyly trait.
Hence, the percentage of the offspring of the couple that would be expected to be polydactyly is 100%