Thinking Mathematically (6th Edition)

$283$ people liked to ski or snowboard.
If $A$ is the set of people who liked to ski, and $B$ is the set of people who liked to snowboard, then: $n(A)=178$ people liked to ski. $n(B)=154$ people liked to snowboard. $n(A\cap B)=49$ people liked to ski and snowboard. The formula for cardinality of the union of two sets: $n(A\cup B)=n(A)+n(B)-n(A\cap B)$ $n(A\cup B)=178+154-49=283$ $283$ people liked to ski or snowboard.