a= ½+⅙
a=3/6 + 1/6
a=4/6
a=2/3
b=1/6 + 1/3
b=1/6 + 2/6
b=3/6
b=1/2
c=1/2 - 1/6
c= 3/6 - 1/6
c= 2/6
c=1/3
