The Formula dialog box appears as shown. To view all the formulas in the entire table first click into the table. Select Ink Equation from the drop-down Equations menu to get started.
This will bring up the Formula dialog with a default of SUM LEFT.
Takes one argument that must either be a number or evaluate to a number. In older versions of Word this appears as the Layout tab of the Table Tools contextual tab in the Ribbon. To insert the bookmark variable in the text do the following. On the Table Tools Layout tab in the Data group click Formula.