The number of people who participate in the calligraphy group accounts for 2/3 of the class, and the number of people who participate in the painting group accounts for 2/5 of the class. Together, it exceeds Unit 1, because five people participated in both events, and neither group participated except two. It can be understood that the excess is the ratio of 5-2=3 people in the whole class. Then we can know the number of students in the class.
(5-2)/(2/5+2/3- 1)
=3/( 1/ 15)
=45 people
There are 45 students in this class.