To create a formula,

select the cell where you want to see your answer.

At the top of your screen,

click on the white bar next to the "fx" sign.

This is where the formulas are stored for each cell.

You'll be able to write formulas here

as well as edit them.

Let's use a formula to add up how much stock we have.

First, double-click where you want the total,

and then type the equation in the "fx" bar.

Always start a formula with an equals sign

followed by the formula instruction.

Type "="

followed by "SUM" in capital letters

followed by "("

followed by the range.

Our range is from D5 to D13,

as these are the numbers we want to total.

So we'll type "D5:D13"

followed by a closed bracket sign

to complete the equation.

Press enter.

If the formula has been entered correctly,

the total will immediately be shown in the cell.

If you've made a mistake,

perhaps you've misspelled something,

an error symbol will appear, like this.

Then you should go back to your "fx" bar,

and you can edit it until it's correct.

You can learn how to create other formulas

by learning the Google Sheets language.