This method works in Office 2010 2013 and 2016. Choose Insert Equation and select Insert New Equation from the bottom of the built in equation gallery. Tap Home and select Insert.
There are multiple equations in the drop-down list then scroll down and select one of them to meet your actual needs.
Select the equation you want to add. We can select to include the chapter number where the chapter starts with heading 1 numbering and use the separator as period. Using the mouse or other input device to write your equation in the light yellow grid area. Depending on the size of your screen you may have to click the Data button first.