21. An English teacher decided to give a second test over the same material as a first test. To reward those students who did well and to provide an incentive to students to improve their score, he announced that he would calculate the combined test score by starting with the first test score and adding of the increase in test score from their first test to their second test. Trish scored 57 points on her first test and 72 points on her second test. What is her combined test score?