Is that wyandotte a large fowl? Did tractor supply happen to have Cornish crosses? If not what else did they have?
It's hard to say yet and of course it's not the best picture but my current guess is probably Cornish cross. Which is a meat breed.
Any one else have any guesses?
I would suggest keeping a close eye on it and doing some research. Possibly call and ask if it's possible. If that's a Cornish X you need to decide what you want to do Cornish X's are meant to be processed out by 8 weeks generally. They need to have feed restricted after I think it's a week or two. They can develop health problems quite easily.
I would suggest posting in the what breed is this area on the thread and seeing what you're told. Also do some research on Cornish X's to decide what your plans are. They're normally sold straight run but I have heard of some people carefully keeping pullets alive for a while to use in a breeding program.