Where is the loot_tables folder?
Solution 1:
The assets are in the respective JAR file in .minecraft/versions/<version>/<version>.jar.
(On Windows 10, hold the windows button and press 'r'. type in '%appdata%', then navigate to '.minecraft', but this depends whether you are using the default launcher or something else like Curse).
Opening that with an archive manager (7-zip, WinRAR etc) will give you the internal folder structure.
Navigate to assets/minecraft/loot_tables. There they are.