$$7\div(7+21)=25\textbackslash\%$$. 
A sugar solution is made by mixing $$7$$ grams of sugar and $$21$$ grams of water. Find the percent concentration of the solution. 
[A] $$20$$\% 
[B] $25$\% 
[C] $30$\% 
[D] $33.3$\% 