Mr. Smith and Mrs. Smith both try to make a drink by combining a few carbonated drinks. Mr. Smith mix a $300$ mL drink that is $50 \%$ sugar and $600$ mL drink that is $20 \%$ sugar. Meanwhile, Mrs. Smith mix a $700$ mL drink that is $10 \%$ sugar and a $300$ mL drink that is $x \%$ sugar. They end up with the same sugar percentage. What is $x$ (rounded to the nearest two decimal places) ? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages