What is $$40\textbackslash\%$$ of $$28.5$$ plus $$28.5\textbackslash\%$$ of $$60$$? ． 
Overseas Competition->Knowledge Point->Calculation Modules->Decimals->Extracting Common Factors from Decimals
It is a general rule that $$x\textbackslash\%$$ of $$y$$ equals $$y\textbackslash\%$$ of $$x$$. This is because $$x\textbackslash\%$$ of $$y= \frac{x}{100} \times y= \frac{xy}{100}$$ and $$y \textbackslash\% $$ of $$x= \frac{y}{100} \times x= \frac{yx}{100}$$.  So $$40\textbackslash\%$$ of $$28.5$$ plus $$28.5\textbackslash\%$$ of $$60 = 40\textbackslash\%$$ of $$28.5$$ plus $$60\textbackslash\%$$ of $$28.5 = 100\textbackslash\%$$ of $$28.5 = 28.5$$. 