Write your two numbers, one under the other. Make sure the digits line up. Draw a line under the number to be subtracted and a "-" symbol to the left of that number. For example, for 712 - 354, you would write 712 above 354, making sure the 2 in 712 lines up with the 4 in 354, the 1 in 712 lines up with the 5 in 354, and the 7 in 712 lines up with the 3 in 354. You would then draw a line under 354 and place a "-" symbol to the left of the 3.
Subtract the two numbers one digit at a time, starting at the ones column to the far right. For example, in 712 - 354, begin by subtracting the 4 in 354 from the 2 in 712. Write your answer under the line in the ones column. If the number you are subtracting is bigger than the number you are subtracting from, you must borrow from the tens place to make the top digit bigger than the bottom digit. To do this, reduce the digit in the tens place of the top number by 1 and add 10 to the digit in the ones place in the top number. For example, in 712 - 354, subtract 1 from the 1 in 712 to make 0 and add 10 to the 2 in 712 to make 12. To show this, cross out the 1 in 712, replace it with a 0, and add a 1 in front of the 2. Subtract 4 from 12 to get 8 in the ones place of the answer below the line.
Repeat Step 2 for the tens- and hundreds-place digits. The number you formed under the line is the answer. In the example, 712 - 354 would equal 358.