Answer:
The angular speed of a point on Earth is
π12
radian per hour. The Equator lies on a circle of radius approximately 4000 miles. Find the linear velocity, in miles per hour, of a point on the Equator.
Step-by-step explanation:
The cardinality of the union between two sets is given by

In fact, if an element is in both A and B, it is counted in both N(A) and N(B), so we're counting it twice. By subtracting the cardinality of the interserction, we're taking back one of these "extra-counted" element, and the count is correct. In your case, the numbers are

This means that the two sets cover, without repetitions, 43 of the 66 elements in the sets. So, there are

elements which are in neither A nor B
Answer is 21.4 %
Used a probability tree diagram.