Repeat the step 1 for every bookmark variable that you want to define. Under Table Tools on the Layout tab in the Data group click the Formula button. If you see Microsoft Equation 30 or Math Type in the Objects list select it to insert an equation.
Then find Ink Equation button at the left side of the Equation Tools Design tab to invoke the handwriting window.
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. Under Table Tools on the Layout tab in the Data group click the Formula button. 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. View Formulas in a Table in Word.