Cosmetic suggestions

Good job, Colin. :sparkles:

This pull request contains mostly cosmetic suggestions. My only comments are:

* Less unnecessary parenthesis :wink:
* Watch your whitespace :space_invader:
* `puts` doesn't need an argument to display a blank line :zap:

All solutions look correct to me. 

* Nice use of underscores for the integer literal in question 4. It really helps readability.
* Same goes for the string interpolation in question 5.
* Clever way of determining the line width programmatically in question 8.