Since we know the ratio is 2:1, then to find the number of students who like iced tea we convert the ratio to a fraction:
this means that one of two students preferred iced tea.
To find the number of students who prefer iced tea we multiply the total number of students by the fraction, then:
Since we can't have a fraction of a student, we conclude that 19 students prefer iced tea and 20 prefer lemonade.