students that own a cell phone but don't own an MP3: 78 - 57 = 21
total number of student with no cell phone: 13 + 9 = 22
total number of student with a MP3 player: 57 + 13 = 70
total number of student without a MP3 player: 21 + 9 = 30
total number of students: 70 + 30 = 78 + 22 = 100
MP3 player no MP3 player Total
cell phone 57 21 78
no cell phone 13 9 22
Total 70 30 100