Hexadecimal
I wish schools would teach math in hexadecimal and floating point numbers, rather than the cryptic base 10 math they commonly use that requires hours of painful learning non-sensible multiplication tables.
Hexadecimal math is so easy. You really have to memorize how to convert 16 hexadecimal digits into binary, then all binary math is super simple – every answer is just 0 or 1, carrying your digit to the next digit if necessary.
But then again, I am a proponent of adapting the KODAK calendar and Celsius, which are far simpler and more rational ways of tracking time and temperature.