Multiply the value of the percentage by the original number. For example, if you are attempting to subtract 40 percent from 200, first multiply 40 by 200 to obtain a product: 40 x 200 = 8,000.
Divide the product by 100 to obtain the value represented by the percentage. For example, to find 40 percent of 200, divide the product (40 x 200) by 100 to produce a quotient of 80 (8,000/100). In this example, the value of 80 represents 40 percent of the original number 200.
Subtract the value represented by the percentage from the original number. For example, when subtracting 40 percent from 200, deduct the value represented by 40 percent from 200. The result is 200 -- {(40 x 200)/100} = 200 -- {80} = 120.