$55=5\times 11$  $100=2\times 2\times 5\times 5$  Because $B$ is the factor both number contains, $B=5$  Thus, $A=11$, $C=20$. 
There are three whole number $A$, $B$, $C$. $A\times B=55$, $B\times C=100$. $A+B+C=$~\uline{~~~~~~~~~~}~. 
  - $$30$$ 
  - $$32$$ 
  - $$34$$ 
  - $$36$$ 