How do I line up equations one below the other to show subtraction or addition?
Use the color(white) tag or quotation marks with spaces to add whitespace.
See this question for more details.
You can also use tabs if that will help line up things
This is for more of a table look, but @Stephan V. cleaned up a table for me using the tab character ">".
This has no tabs
">"This will have one tab
This now has one tab
This has two
And so on...
The example of the table is in this question - hit edit to see the use of the tabs: