12. (Level 2) Among the 90 students in a dormitory, 35

own an automobile, 40 own a bicycle, and 10 have

both an automobile and a bicycle. Use a box model

to find the number of the students who:

(a) do not have an automobile.

(b) have neither an automobile nor a bicycle.

(c) have an automobile or a bicycle, but not both.

Answer: 55, 25, 55