Two friends, alejandro and mia, agreed to split the check at a restaurant. alejandro ordered $12 worth of food and mia ordered $18 worth. at the end of the meal, alejandro put his $12 contribution on the table, plus a $20% tip on his bill and mia put her $18 contribution on the table, plus a $15% tip on her bill. the total tip left by alejandro and mia is equal to r% of the total check for their table, where the "total check" amount does not include the tip. what is r?