To create your own select Design Equation Ink Equation. When you embed an Excel worksheet into a Word document you can either copy and paste from Excel to Word or embed using the Paste Special feature. This will bring up the Formula dialog with a default of SUM LEFT.
On the Table Tools Layout tab click the Formula button.
Typing the formula that you want to use in the formula box. You can use simple formulas in Microsoft Word such as addition subtraction - multiplication or division. To add a formula into the Word table see How to calculate formulas in a Word document if you need to use formulas without tables do the following. Word contains a powerful to allow you to build Excel-like formulas in your Word documents.