Right now I am thinking 2.  

What is the difference between a letter and a number and what is the difference between literature and mathematics? 

The main difference between a letter and number is that a letter is a symbol but a number is an idea.

Symbolic uses of letters stand for sounds in speech, where as numbers are concepts symbolized by numerals. Numbers help us to express or measure the quantity of object, while letters, help us to communicate information through writing or speech. 

So to take that to the next step, literature are groups of letters made up to sympbolize words that tells a story. It uses characters, plots, figure of speech and emotional connections to keep the reader caring about what they are reading. The reader feels alive because of the flowing, pulsing ideals of those words. Mathematics has not time for emotion. There is no story, no personality, it is a science and the framework for all other sciences. Mathematics makes numbers practical and help us with new discoveries.