Formulas

Hi Lucy, Thank you for your post, and welcome to the forum;
In answer, the most helpful way of building a formula is to use the fx button on the Formula Bar. This will open a dialog box which will allow you to choose from a multitude of Formulas, (just type your requirement, and Excel will attempt to match your needs).
You can then enter values or cell references to build the formula.
I hope that helps, if so please click the resolved link, regards Pete