To subtract two or more numbers in Excel you need to create a formula.
The important points to remember about Excel formulas include:
 Formulas in Excel always begin with the equal sign ( = );
 The formula is always typed into the cell where you want the answer to appear;
 The subtraction sign in Excel is the dash (  );
 The formula is completed by pressing the Enter key on the keyboard.
Using Cell References in Formulas
Although it is possible to enter numbers directly into a formula (as shown in row 2 of the example), it is usually much better to enter the data into worksheet cells and then use the addresses or references of those cells in the formula (row 3 of the example).
By using cell references rather than the actual data in a formula, later, if it becomes necessary to change the data, it is a simple matter of replacing the data in the cells rather than rewriting the formula.
The results of the formula will update automatically once the data changes.
Another option is to mix cell references and actual data (row 4 of the example).
Adding Parenthesis
Excel has an order of operations that it follows when evaluating which mathematical operations to carry out first in a formula.
Just as in math class, the order of operation can be altered by using parenthesis as the examples shown in rows five and six above.
Subtraction Formula Example
As seen in the image above, this example creates a formula in cell D3 that will subtract the data in cell A3 from the data in B3.
The finished formula in cell D3 will be:
= A3  B3
Point and Click on Cell References
Although it is possible to just type the above formula into cell D3 and have the correct answer appear, it is better to use point and click to add the cell references to formulas in order to minimize the possibility of errors created by typing in the wrong cell reference.
Point and click involve clicking on the cells containing the data with the mouse pointer to add the cell reference to the formula.

Type the equal sign ( = ) into cell D3 to begin the formula.

Click on cell A3 with the mouse pointer to add that cell reference to the formula after the equal sign.

Type a minus sign (  ) after the cell reference.

Click on cell B3 to add that cell reference to the formula after the minus sign.

Press the Enter key on the keyboard to complete the formula.

The answer 5 should be present in cell D3.

Even though the answer to the formula is shown in cell D3, clicking on that cell will display the formula in the formula bar above the worksheet.

You now know the key methods for using cell references.
Changing the Formula Data
To test the value of using cell references in a formula, make a change to the number in cell B3 (such as going from 5 to 4) and press the Enter key on the keyboard. The answer in cell D3 should automatically update to reflect the change in data in cell B3.
Creating More Complex Formulas
To expand the formula to include additional operations (such as division or addition) as shown in row seven, just continue to add the correct mathematical operator followed by the cell reference containing the new data.