Let x represent the number of students who liked both chocolate and vanilla ice cream. With this, the number of students who liked chocolate ice cream alone is 140 - x. Similarly, the number of students who liked vanilla ice cream only is 120 - x. The total number of students is 220.
x + (140 - x) + (120 - x) = 220
The value of x is 40. Thus, 40 students liked both chocolate and vanilla.
