Unlike addition, the order of subtraction DOES make a difference. For instance, 3.9 - 0.9 is NOT the same as 0.9 - 3.9. Subtraction is the opposite of addition, so you can check your answers to subtraction problems using addition. Look at the example below:
0.9 - 0.2 = 0.7
Checking by addition:
0.7 + 0.2 = 0.9
Tip: You may prefer to use a calculator and/or paper & pencil to assist you. There is an on-screen calculator available from
Start > Programs > Accessories > Calculator.