A survey shows that 80% of all households have a colour television and 30% have a microwave oven. If 20% have both a colour television and a microwave, what percentage has neither? In a group of 50...

A survey shows that 80% of all households have a colour television and 30% have a microwave oven. If 20% have both a colour television and a microwave, what percentage has neither?

In a group of 50 students, 30 study French or German. If 20 study French and 15 study German find the probability that a student studies French and German.