Final answer:
With the information given, it is impossible to determine the exact number of chickens Old McDonald has among the 47 barnyard animals, as we lack data to differentiate between chickens and sheep.
Step-by-step explanation:
The question is asking us to determine how many chickens Old McDonald has if he has a total of 47 barnyard animals consisting entirely of chickens and sheep. This problem can be solved using a system of equations or algebraic expression because we have two types of animals that make up a total. Without additional information that differentiates between the number of chickens and sheep (such as the total number of legs), we cannot solve this problem with the given data. Therefore, there isn't enough information provided to determine the exact number of chickens.