just multiply the top number by the top number and the bottom numbers by the bottom numbers so
2/4 times 1/3=(2 times 1)/(4 times 3)=2/12
so to simplify, we find the ones exg 4/8=1/2 because 1/2 times 4/4=4/8 and 4/4 cancels out so
2/12=2/2 times 1/6
=1/6