$$10\times20\textbackslash\%+40\times 25\textbackslash\%=12$$ ounces.  $$(10+40)-12\div40\textbackslash\%=20$$ ounces. 
Amy mixes $$10$$ grams of a $$20\textbackslash\%$$ sugar solution and $$40$$ grams of a $$25\textbackslash\%$$ sugar solution together. After~\uline{~~~~~~~~~~}~of water evaporates, the percent concentration of solution is $40\textbackslash\%$. 
Options:
(A) $$15$$ grams 
(B) $$18$$ grams 
(C) $$20$$ grams 
(D) $$25$$ grams 