You can practice using this live spreadsheet:
Let's add 2 + 2
Now go to cell C3 and type:
= 2 + 2
You should see the number 4.
Formulas can also reference other cells:
Go to cell B4 and write a formula with reference to cell B3
You should see the error: #VALUE!
This means that cell B3 contains labels. Therefore, referenced cell must contain a value.
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