Answer:
There is a 50% chance the kids will have Hitchhiker's thumb
Step-by-step explanation:
Because Hitchhiker's thumb is dominant and the woman doesn't have it it's safe to assume her genes for it are hh. In a punnet square it would look like
h h
H | Hh Hh
h | hh hh
If that makes any sense I hope it does
Point is, 2 of the 4 boxes would say Hh and the other two would have hh