Two friends, Alejandra and Mia, agreed to split the check at a restaurant. Alejandra ordered $12 worth of food and Mia ordered $18 worth. At the end of the meal, Alejandra put her $12 contribution on the table, plus a 20% tip and Mia put her $18 contribution on the table, plus a 15% tip. The total tip left by Alejandra 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?