1. Fix code solution (it used the assignment operator to compare _a_ and _b_ instead of the comparison one; which wouldn't pass the test at the exercise page).
2. Add problem explanation, hint, code explanation, run example and resources
* Translate challenge subtitles and example challenge text to Spanish
* Corrected errors in syntax and punctuation
* Multiple corrections of it/s to its plus other grammar corrections
* Correction and added paragraph to CSS Flex article
* Corrected my own typo
* Corrected capitalization, American spellings and typos
* [Guide] Basic JS: Random numbers within range. Enhancements
Added code solution, explanation, resources and other minor fixes.
* Additional fix; list.
* update: created ordered list of calculation
