Some errata fixes.

There appeared to be an unexplainable issue concerning the layout file activity_calculator.xml (see picture).
![Screenshot 18 ](https://f.cloud.github.com/assets/3958771/376996/efb469c0-a46c-11e2-9e62-cada8b225ab5.png)
I did an attempt to fix some of
them, but it might not be perfect. Also, I dealt with toxic code again, but this was not like before where it took me about an hour of my coding time to delete them.

This is the first pull request you are dealing with. Do you remember what to do?