Thinking Mathematically (6th Edition)

$(A\cap C)'$ is the set of all numbers that are not both a natural odd number and less than $9$ and a number that is both natural and less than $6$ and greater than $1$. Thus $(A\cap C)'$ is the set of numbers in $U$ that are not in $\{3,5\}$Thus $(B\cap C)'=\{1,2,4,6,7,8\}$.