In a class of pupils, $80\textbackslash\%$ participated in basketball, $85\textbackslash\%$ participated in football, $74\textbackslash\%$ participated in softball and $68\textbackslash\%$ participated in squash. Find the minimum percentage of pupils who participated in all the four sports events. 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Finding the Rate
Least percentage of pupils who participated in both basketball and football  $=80\textbackslash\%+ 85\textbackslash\%-100\textbackslash\% =65\textbackslash\%$,  Least percentage of pupils who participated in basketball, football and softball  $=65\textbackslash\%+74\textbackslash\%-100\textbackslash\% =39\textbackslash\%$,  Least percentage of pupils who participated in basketball, football, softball and squash  $=39\textbackslash\%+ 68\textbackslash\%-100\textbackslash\% = 7\textbackslash\%$. 