We know that any number is divisible by 9 if sum of the digits of the number is divisible by 9. Now sum of the digits from 0 to 9 =0+1+2+3+4+5+6+7+8+9=45 Hence to form 8 digits numbers which are divisible by 9 , a pair of digits either 0 and 9,1 and 8,2 and 7,3 and 6 or 4 and 5 are not used.
Digits which are not used to form 8 digits number divisible by 9
Number of 8 digits numbers which are divisible by 9
0 and 9
8 x 7!
1 and 8
7 x 7!
2 and 7
7 x 7!
3 and 6
7 x 7!
4 and 5
7 x 7!
Hence total number of 8 digits numbers which are divisible by 9 =8×(7!)+7×(7!)+7×(7!)+7×(7!)+7×(7!) =36×(7!)