The following image was made by Subtract Fractions Designer:
The parts of a subtraction example are the minuend, the subtrahend, and the difference.
When the program starts, you will be asked to identify the minuend and then the subtrahend. Yu will be asked to find the difference when the minuend and subtrahend are correctly identified.
You can see from the picture that the minuend is 4 1/8 units in length and the subtrahend is 3 7/8 units in length. The difference will be the distance from the end of the subtrahend to the end of the minuend for 2/8 units.
In many examples, the difference may be found visually by determining the distance from the end of the subtrahend to the end of the minuend. In the above example you can see that there are only 2/8 units from the end of the subtrahend to the end of the minuend.
When calculating some subtraction examples the numerator of the subtrahend is larger than the numerator of the minuend. In that case you may rewrite the minuend to subtract. Some texts call the procedure "borrowing". To borrow, simply decrease the whole number 3 by 1. Then add 8/8 to 1/8 to get 9/8, giving the fraction 3 9/8.
Notice how 4 1/8 is renamed as 3 9/8 so that the numerators can be subtracted.