qa
answer
= 13C2 * 7C1 + 13C1 * 7C2
= 78*7 + 13*21
= 819
qb
answer
= 10C1 + 10C2 + 10C3
= 10 + 45 + 120
= 175
qc
10
= (3,3,1,1,1,1) [2 with 3 toppings and 1 topping on the rest]
= (3,2,2,1,1,1) [1 with 3, 2 with 2 and 3 with 1 topping]
= (2,2,2,2,1,1) [2 with http://charleswilhelmblog.blogspot.com/ with 1 topping]
answer
= 10C3 * 7C4 * (4C2)/2! * 3C3
= 10!7!4!3!/7!3!4!3!2!2!3!*2
= 12600
case 3 : [2 with 1 topping and 2 toppings on the rest]
answer
= 10C2 * [8C2*6C2*4C2*2C2]/4!
= 10!/2!2!2!2!2!*4!
= 4725
https://ca.answers.yahoo.com/question/index?qid=20080618143845AA9MQ7H
bob8lee6 Community Member 
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