It's simple. Just use an EXCEL spreadsheet. After the original price is filled in, enter the = sign in the blank box, then press and hold the Shift key and the number 8 key (that is, the multiplication symbol *), and then enter the number you want to discount (for example, your original price is 100, and now you want to give a 20% discount, you can enter 8, and the blank box is 100*8), and then press the Enter key, so that your menu can be discounted. I don't know if you are familiar with EXCEL, but it will be easy to understand if you can use it. I hope I can help you.