其它
There are three whole numbers $A$, $B$ and $C$ $(B\ne 1)$. $A\times B=15$, $B\times C=35$. $A+B+C=$~\uline{~~~~~~~~~~}~. 
Overseas Competition->Knowledge Point->Number Theory Modules->Prime Factorization
$15=3\times 5$  $35=5\times 7$  Because $B$ is the factor both number contains, $B=5$  Thus, $A=3$, $C=7$,  $A+B+C=15$. 