Subtracting decimals involves writing the two decimals one below the other and making sure that the decimal points line up before subtracting in the normal manner. However, the larger decimal should be placed above the smaller one. Similarly, if the two decimals do not have the same length, then add zeroes before subtracting them.
Adding extra zeroes to a decimal is especially useful when regrouping or borrowing. An example of this is to subtract 1.223 from 3.8. To perform the subtraction, add two zeroes to 3.8 so that it reads 3.800. Place 1.223 directly below 3.800 (the larger decimal) and make sure that the decimal points line up before subtracting the decimals. The zeroes are added so one can borrow from the digits to the left of the first zero. The answer to 3.800 - 1.223 is 2.577.