You use formulas to perform mathematical functions on cells. There are two basic ways of writing formulas available: “ranged syntax” or “simple syntax.” A “syntax” is simply a way of expressing or writing something. It is important to note that these two syntaxes are not mutually exclusive! In fact, your more complex formulas will often incorporate elements of both to arrive at the desired result. Typically, you will use the simple syntax to perform multiple mathematical calculations on multiple cells. You use the ranged syntax to perform a single mathematical function over multiple cells.
To write a formula, first click into the cell where you want the results of the formula to appear. Next, write your formula. When you are finished, exit the cell to display the answer to the formula that you wrote. Once again, this is the concept of “content versus display” at work. The actual content of the cell will be the formula, but the cell will display the answer to the formula. If you click into the formula cell after it has been created, you will see the actual formula displayed in the Formula Bar and the answer displayed in the worksheet. To show the actual formulas in the worksheet, you can press the “Ctrl” key and the ` (single left quotation mark) key.
Check out this video clip on writing formulas in Microsoft Excel 2013: