Select Insert to bring your equation into the file. Select the table cell where you want your result. This tutorial demonstrates how to write a math equation using Microsoft Word 2010.
Click on the word yields and replace it with as many spaces as you need to create an arrow of whatever length you want.
To get a long arrow click on the operator button and choose the arrow with the word yields written over it under common operator structures. Select the table cell where you want your result. Insert symbols by typing symbolname and press the space bar. Click in a cell that should contain the sum of the rows.