Q:A class of 25 students has options as to which science subjects they study. The options are biology, chemistry, geology and physics. 15 of the 25 students took only two of these sciences, whilst the other 10 students took three. 5 students studied geology and 8 studied biology, but nobody took both. How many students studied chemistry, given that they all also took physics?
I know that n(G)=5,n(B)=8,n(BnG)=0,n(BnCnGnP)=0, there is no one who takes only 1 subject and no one who takes all 4 subjects. Students who take chemistry will also take physics.I also know that n(CnP)=n(BnCnP)+n(PnCnG)=10. So how can I get the n(C)?