The Vennville junior hockey team has 12 members who can play forward, 8 who can play defence, and 2 who can be goalies. What is the smallest possible size of the team if
a) no one plays both defence and forward?
b) three of the players are able to play defence or forward?
c) both the goalies can play forward but not defence?
i don't understand how the answers in the back of my text are derived. a) 20 b) 19 c)20