Form the greatest and the smallest number using the following digits only once.

$3, 2, 1, 9$

Form the greatest and the smallest number using the following digits only once.

$9, 6, 0, 7$

Write the greatest $4$-digit number by changing the position of digits in the number $3175$.

Write the greatest $4$-digit number by changing the position of digits in the number $6471$.

Write the greatest $4$-digit number by changing the position of digits in the number $4156$.

Write the greatest $4$-digit number by changing the position of digits in the number $4449$.

Write the greatest $4$-digit number by changing the position of digits in the number $7650$.

Write the greatest $4$-digit number by changing the position of digits in the number $9863$.

Write the greatest $4$-digit number by changing the position of digits in the number $8144$.