3/6 divide numerator and denominator by 3 and get 1/2
12/20 divide the numerator and denominator by 2 ,and get 6/10 divide by 2,and get a final answer of 3/5.
8/24 divide the numerator and denominator by 8 ,and get 1/3.
30/40 divide the numerator and denominator by 10 ,and get 3/4
I hope this helps you,and good luck.