How to Write Formulas in Excel 2013
Excel formulas can do everything that a basic calculator can do, so if you’re in a hurry and don’t want to pull up the Windows Calculator application, you can enter a formula in Excel to get a quick result. Experimenting with this type of formula is a great way to get accustomed to formulas in general.
Excel also has an advantage over some basic calculators (including the one in Windows): It easily does exponentiation. For example, if you want to calculate 5 to the 8th power, you would write it in Excel as =5^8.
Just as in basic math, formulas are calculated by an order of precedence. The table lists the order.
Order  Item  Example 

1  Anything in parentheses  =2*(2+1) 
2  Exponentiation  =2^3 
3  Multiplication and division  =1+2*2 
4  Addition and subtraction  =10–4 
In this exercise, you learn how to enter some formulas that perform simple math calculations.

Launch Excel if needed and open a new blank workbook. If you already have another workbook open, press Ctrl+N to create a new workbook.

Click cell A1, type =2+2, and press Enter.
The result of the formula appears in cell A1.

Click cell A1 again to move the cell cursor back to it; then look in the Formula bar.
Notice that the formula you entered appears there, as shown in this figure.

Click cell A2, type =2+4*3, and press Enter.
The result of the formula appears in cell A2.
In this case, because of the order of operations, the multiplication was done first (4 times 3 equals 12), and then 2 was added for a total of 14.

Press the uparrow key once to move the cell cursor back to A2 and examine the formula in the formula bar.

In cell A3, type =(2+4)*3 and press Enter.
In this case, the parentheses forced the addition to occur first (2 plus 4 equals 6), and then 3 was multiplied for a total of 18.

Press the uparrow key once to move the cell cursor back to A3 and note the formula shown.

Close the workbook without saving changes to it.