How many 3 digit numbers can be created where one of the digits is 6 and the sum of the digits is 18? ( digits can be repeated)

615,624,633,642,651,165,264,363,462,561,156,246,336,426,
516,426,246,651,642,624,615,561,462,264,165.
I think more than this no possibilities are available.

Let's list the requirements:

Every number you create must have 3 digits.
These 3 digits must add up to 18.
One of the digits is 6.
Digits can be repeated.

Try some of the easier numbers first.  If one digit is 6, and the other two digits add up to 18, then possibilities include 666 (6+6+6=18, as required).

933 won't work, because it doesn't contain a 6, as required.

163 won't work, since the digits don't add up to 18.

See the pattern here?

What about 684?  Do the digits add up to 18?  does 684 include a 6?
What about 864?   Same questions...
Please experiment with this for a while.  Then count the possibilities you have identified.