A feast is organised for a group of 100 people. In this feast 50 people do not like fish and 60 people like chicken. 10 people like neither fish nor chicken. How many people like both fish and chicken ?

Number of people who like fish = 50

Number of people who like chicken = 60

Let the number of people who like both fish and chicken = x

Number of people who do not like fish = 50

Number of people who do not like chicken = 100 - 60 = 40

Number of people who do not like either fish or chicken = 10

So, number of people who do not like either fish or chicken or both = 40 + 50 - 10 = 80

Number of people who like at least one of the two dishes = 50 + 60 - x = 100 - Number of people who do not like both the dishes = 100 - 10 = 90

=> x = 20

So, 20 people like both the dishes