The number of triplets $(x, y, z)$. where $x, y, z$ are distinct non negative integers satisfying $x+y+z=15$, is

The number of ways in which we can select three numbers from $1$ to $30$ so as to exclude every selection of all even numbers is

A box contains two white balls, three black balls and four red balls. In how many ways can three balls be drawn from the box if at least one black ball is to be included in the draw

${ }^{n-1} C_r=\left(k^2-8\right){ }^n C_{r+1}$ if and only if:

How many different words can be formed by jumbling the letters in the word $MISSISSIPPI$ in which no two $S$ are adjacent $?$