I read mon's reply after I'd already typed mine, so I'll add a few notes:
Efofex is the math program kids use once they reach pre-algebra and are starting to type equations. There are free trials and you can get it free for 10 years with a letter verifying disability. It is an add in for word so goes right into the word documents. However, my stick in the mud prefers to not use it in word and to save as a PDF directly from Efofex. It should be available for Macs within the next couple of years. They are still developing it.
There are a few Efofex modules already in production for Macs, and it runs really well. Prior to the Mac modules being released, my ds ran Efofex on his Mac laptop by using Parallels to run Windows (can't remember which version of Windows), and Efofex ran on the Windows OS.
For elementary school math, there's nothing yet that lines up the numbers for you.
This is exactly what MathPad Plus does. As I mentioned, we never used it, so I can't tell you anything about it from personal experience, but it was recommended to us for this purpose. I think I've seen similar attempts on a few iPad apps, but nothing that our ds was interested in using.
polarbear