Answer:
0.3043 or 30.43%
Explanation:
I think what you are asking is what is the chance of her choosing a chicken? if so, just take the number of chicken divided by the total number of animals.
7 divided by 23 = 0.3043
you could also take the chance of choosing any animal ( 1 out of 23 ) and multiply by how many chickens there are too, but that is a bit more messy with the decimals.