What formulas would I use to calculate the two following problems:

1) What percentage is n$ of x?

2) What amount is y% of x?

Both of these should work together - for example, if the "x" value is 100,
then:

1) 25 of 100 is 25%

and

2) 25 is the value of 25% of 100

I need the two separate calculations that I can use in excel -- assuming
that the "x" value is constant, and the n and y values will be entered by
the user.

Thanks in advance!