base 12 is a positional numeral system with twelve as its base. It uses 12 different digits for representing numbers. The digits for base 12 could be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a, and b.

base 9 is a positional numeral system with nine as its base. It uses 9 different digits for representing numbers. The digits for base 9 could be 0, 1, 2, 3, 4, 5, 6, 7, and 8.