In how many ways can the letters of the word DELHI be arranged, keeping the positions of vowels and consonants unchanged?

What is the number of positive integer solutions of $x+y+z=5$?

If the number of selections of r as well as $(n+r)$ things from 5n different things are equal, then what is the value of r?

What is the number of selections of at most 3 things from 6 different things?