A survey in a class shows that 14 of the student plays football,10 plays handball and 5 play both football and handball . How many student are there in a class if every one plays at least one of this game.
Number(football OR handball) = Number(football) + number(handball) - number(football AND handball)
= 14+10-5 = 19
or make a Venn Diagram and fill in the values.