At a country club 35 people play golf, 28 swim, and 24 play tennis. Of
these, 6 play golf and tennis only, 9 play golf and swim only, and 7 play
tennis and swim only. 8 people do all three. How many members are there
altogether?

A student struggles to draw a Venn diagram that represents the union and intersection
of three sets or their complements. Before walking through an illustrated example,
Doctor Peterson shows how to take apart such problems, then concludes with how to
check your work.