Based on a survey of 200 students, 140 students like cold drinks, 120 students like milkshakes, and 80 students like both. How many students like at least one of the drinks?

Let $C$ be the set of students who like cold drinks and $M$ be the set of students who like milkshakes.
Given values:
$n(C)=140$
$n(M)=120$
$n(C\cap M)=80$

The number of students who like at least one of the drinks is given by the union $n(C\cup M)$:

$$n(C\cup M)=n(C)+n(M)-n(C\cap M)$$

$$n(C\cup M)=140+120-80=180$$