I want to find the number of players taking chemistry, so I'll call that x. The inclusion-exclusion principle says that the total number of people in two groups is equal to the sum of the people in each group minus the people in both groups. Simplifying the equation, I get 12 = 5 + x, so x = 7. That means 7 players are taking chemistry.


At Beaumont High School, there are 12 players on the baseball team.  All 12 players are taking at least one of biology or chemistry.  If 7 players are taking biology and 2 players are taking both sciences, how many players are taking chemistry?