A bag of toffee is $8$ dollars, a bag of cotton candy is $6$ dollars, and a bag of orange candy is $13$ dollars. Now, the candy shop decides to mix $30$ bags of toffee, $50$ bags of cotton candy, and $20$ bags of orange candy for $100$ bags of assorted candy. What should be the price of the assorted candy in dollars to keep the total revenue unchanged? 
Overseas Competition->Knowledge Point->Word Problem Modules->Average Problems 
Total revenue: $30\times 8+50\times 6+20\times 13=800$ dollars  A bag of assorted candy: $$800\div 100=8$$ dollars 