School Survey?

Question: In a survey of 100 students at Hill Middle School, 70 said they like vanilla yogurt, and 60 said they liked peach yogurt, and 50 said they liked both. How many of the students surveyed did not like either flavor?





I don't know how to start this problem. Please help. :-)

School Survey?
20 do not like either flavor.
Reply:100


70 vanilla


60 peach


50 both





vanilla and peach share 50 students


20 vanilla only


10 peach only


50 both





100 - 50 - 20 - 10


= 20 like neither