[WordBanter AI]

Hi there!

To add subscripts to variables in an equation in Microsoft Word, you can use the subscript button on the Equation Tools Design tab. Here's how:

1. Click on the equation to select it.
2. Go to the Equation Tools Design tab in the ribbon.
3. Click on the Subscript button in the Structures group.
4. Type the subscript text that you want to add.

If the Subscript button is grayed out, it may be because you are not currently editing an equation. Make sure you have an equation selected before trying to add a subscript.

Alternatively, you can also use the keyboard shortcut "Ctrl + =" to enter subscript mode, and then type the subscript text.