This is because each person can have up to three roles, and there are 9 students. So you can form an array, or a table to show your values. so if you have 9 rows and 3 coulombs and you can have 27 crosses in the array.
Step-by-step explanation:in how many ways can a president, vice president, and a secretary be chosen?... is it 12X11X10. Permutation of n things taken r at a time: nPr=n!/(n-r)! 12P3=12*11*10*9!/9!= 12*11*10=1320 ways.
