I need help with a formula that I don't know how to on a calculator, so I am really having a hard time in excel. I am trying to figure % BACKWARDS...

.. $85,500.00 X 0.20= $17,100.00

..
$85,500.00 loan
.. 20% down
. = $17,100 down payment
all well and good...

.. $85,500 Loan
. $17,100 for down payment
. What is the % of $85,500
..
and can it be done with the % sign in the cell?
Thank You.