โจทย์เรื่องเซต
80 students are surveyed to determine which of 3 different classes they
would like to take next semester. 23 want to take only Art and 18 want to
take only Business. 8 students want to take both Art and Business.31 want
to take Science. 9 students want to take both Art and Science. 2 students
want to take both Business and Science. 6 students want to take all the
classes.
How many students want to take Science only?