50-10=40；$$40\div$$ 50=0.8；0.8=80\% 
A bag contains $$50$$ straws of two different colours. $$10$$ straws are yellow and the rest are red. What percentage of the straws are red? 

a: $$10\textbackslash\%$$ 
b: $$20\textbackslash\%$$ 
c: $$40\textbackslash\%$$ 
d: $$80\textbackslash\%$$ 