Add 9, 1 / 2 and 3 to make these four numbers form a proportional expression. This number is A54 B6 C1

Add 9, 1 / 2 and 3 to make these four numbers form a proportional expression. This number is A54 B6 C1

a 3:(1/2)=54/9
c 3:9=1/2:1