In a certain country, a part of the residents can speak English only, a part can speak French only and the rest can speak both languages. It is known that $$85\textbackslash\%$$ residents can speak English and $$75\textbackslash\%$$ can speak French. What percent of the residents of this country can speak both English and French? ($$2002$$ Math kangaroo Problem, Level $$7-8$$, Question \#$$17$$) 
Overseas Competition->Knowledge Point->Counting Modules->Inclusion-Exclusion Principle->Inclusion-Exclusion Principle for Two Sets
$85\textbackslash\%+75\textbackslash\%-100\textbackslash\%=60\textbackslash\%$. 