There are two ways to do it.  Multiply then subtract, or subtract 
then multiply.

Method 1:

(a) Figure the dollar discount by multiplying the decimal equivalent 
of the percent off by the original price.
(b) Subtract the result of (a) from the original price.

Method 2:

(a) Subtract the percent off from 100% and get the decimal equivalent.
(b) Multiply the result of (a) by the original price.

The second method is a little easier.  Try both ways.  They will give
you the same answer.

Edwin