In how many ways can we give six identical pens to three students (note that a student can get zero pens)



let a be a set of natural numbers from 1 to 10. how many ordered triples (x, y, z) are there such that x belongs to a, y belongs to a and z belongs to a. also x


in an arithmetic progression, a5+a8+a11=28, and a14+a17+a20 =44. find common difference.