【Answer】 26 people.
【Analysis】Key point: Principle of Inclusion-Exclusion
At least like one channel: 100-3=97 (people), like both channels: $68+55-97=26$ (people).
12. A school's 3rd grade has a total of 100 students, of which 68 love watching sports channels, 55 love watching cultural channels, and 3 students do not love watching either of these channels. So, the number of students who love watching both channels is ( ) people.