Question: how many 6permutations of 15 have their digits listed in...
How many 6-permutations of  have their digits listed in increasing order? Show all your reasoning.
(Note that, in the decimal system, digits are only the symbols 0,1,2,3,4,5,6,7,8 and 9. Therefore, to give an example of which 6-permutations you should be counting in this question, (1,2,4,5,7,8) should be among them, whereas (1,2,4,5,8,13) should not. In this question, 13 read as one-three rather than thirteen, so (1,2,4,5,8,13) is not increasing order. One correct increasing order example you need to count is (1,13,4,5,8,9))