There are seven candidates for $3$ posts. In how many ways can the posts be filled?

How many numbers lying between $99$ and $1000$ can be formed using the digits $2, 3, 7, 0, 8, 6$,if each digit can be used only once in each number?

If the number of five-digit numbers with distinct digits and $2$ at the $10^{\text{th}}$ place is $336k$,then $k$ is equal to

The number of times the digit $3$ will be written when listing the integers from $1$ to $1000$ is

$A$ car can hold $2$ people in the front seat and $1$ person in the rear seat. If among $6$ persons $2$ can drive,then the number of ways in which the car can be filled is

There are $4$ parcels and $5$ post-offices. In how many different ways can the registration of the parcels be made?