We are just adding the fractions.

You can obtain an explanation for any step by clicking on it. Please note that you cannot click on the very first expression, which is the original problem. Quite often, several transformations will be performed within the same step. Use the explanation navigation buttons to step through all of them:

If you are not satisfied with the number of solution steps displayed (either too many steps or too few), click on the Options button to adjust the number of steps to be shown. By applying lot of steps you will get the following solution: