Implementing AVG with SELECT

Hi,

can anyone help me, how to implement AVG aggregate function just with the following statements:

SELECT,[NOT] EXISTS,IN,ALL,ANY,FROM,WHERE,GROUP BY,HAVING,AND,OR

And second question:

How can I, show the first 10 tuple in a table with statements that I mentioned above.

I know my questions can be implemented, but i don't know how.

Thanks for your helping