$35=5\times 7$  $84=2\times 2\times 3\times 7$  Because $B$ is the factor both number contains, $B=7$  Thus, $A=5$, $C=12$. 
There are three whole numbers $A$, $B$ and $C$ ($B
eq1$). $A\times B=35$, $B\times C=84$. $A+B+C=$~\uline{~~~~~~~~~~}~. 
Options:
- $$20$$ 
- $$23$$ 
- $$24$$ 
- $$29$$ 