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Re: Permutation and combination Problems
by Ankit Kaushik - Thursday, 19 November 2015, 03:41 AM
  For the first one try this approach.

we have to find the ways which will make the sum of scores to b 90.Put it another way, we are looking for ways by which one loses 90 marks out of 180 to get net 90 marks.

so, that is way of finding solution for
a + b + c + d = 90 where 0