I have to subtract 5% from a number of differently priced totals, to discover the what the discount is for those totals.

I would like to know how to do this myself, on a calculator, and by using a function key which is the main area of focus for me right now.

As apart of my Business course I must learn all functions on excel, but my dragon lady teacher won't give me the time of day to answer any questions (because she's an angry dragon).

The totals I have to discover 5% of are: $2,647.00, $3,980.50 and $4,000.00

Please help!!