What was the question for this implicit rationale, and corresponding answer?
She has 120 minutes to practice because 2 x 60 = 120. She has already spent 93 minutes on her work because 30 + 25 + 38 = 93. She has 27 minutes to use on finger exercise because 120 - 93 = 27.
 The answer: 27
The question: Joan has 2 hours to get all her music practice done. She spends 30 minutes on the piano, 25 minutes writing music on her computer, and 38 minutes reading about the history of the piano. Her final work is to use a special finger exerciser. How much time does she have left to use this?