1. Excel®

1.12. Formulas

When you need to do a calculation that is different from the AutoSum options, you can create your own formula directly in a cell on the spreadsheet.  

Choose a cell where you would like to display the result of the calculation and click there to begin writing your formula.
The symbols used to write a calculation are similar to those you may have used on a calculator.

Add                    +

Subtract            -

Multiply           x

Divide              \

The difference is that you place the = (equal sign) at the start of the formula.  That symbol tells Excel® that this cell will contain a formula.  

For example, if you wanted to subtract the number in cell C2 from the number in cell C5, you would type =(C5-C2).  Then hit Enter to run the calculation and see your result. 

While you are typing your formula, a little pop-up box may appear which is trying to guess what you are doing.   Since it assumes more complex calculations, you can ignore it and continue to enter your formula.  If you have written the formula incorrectly (e.g. added a space or left out a bracket), a second pop-up may appear that will attempt to auto-correct the formula.