If $\binom{15}{3r} = \binom{15}{r+3}$,then $r = \dots$

The number of integers between $10$ and $10,000$ such that in every integer every digit is greater than its immediate preceding digit,is

If $^{15}C_{3r} = ^{15}C_{r+3}$,find the value of $r$.

At an election,a voter may vote for any number of candidates,not greater than the number to be elected. There are $10$ candidates and $4$ are to be selected. If a voter votes for at least one candidate,then the number of ways in which he can vote is:

In how many ways can $5$ letters be selected from the letters of the word $INDEPENDENT$?

In an election,there are $8$ candidates,out of which $5$ are to be chosen. If a voter may vote for any number of candidates but not greater than the number to be chosen,then in how many ways can a voter vote?