You can multiply 23.67 by .2 (this will give you 20% of 23.67 which happens to be 4.734). Then you would subtract 4.734 from 23.67 giving you 18.936, or for monetary purposes about $18.94. Or, if you are in a hurry or simply wish to take a shortcut, getting 20% off is just like paying 80% so you can multiply 23.67, or any other number you need, by .8 and you will get 18.936.
In summation, if you take the percentage you have to pay (100-percentage off), then move the decimal 2 decimal places (like from 80 to .8), then multiply this by the price you will get the sale price.
20 percent off of 750 is 600.
20 percent off 249 = 199.20
20 percent off of 30 is 6.
20 percent off of 28.95 is 5.79.
79.6 is 20 percent off of 398.
64 is 20 percent off of 320.
20 percent off of 390 is 78.
20 percent off of 25.95 is 5.19.
20 percent off from 95.49 is 19.098.
20 percent off of 34.00 is 6.80.
20 percent off of 229.99 is 45.998.
20 percent off of 695 is 556.