Draw three circles such that each intersects the other two for your diagram. You will see that $3$ played only rugby, $11$ played only cricket and $10$ played only football. Try to fill in numbers into the regions one by one.
Draw three circles such that each intersects the other two for your diagram. You will see that $3$ played only rugby, $11$ played only cricket and $10$ played only football. Try to fill in numbers into the regions one by one.