In order to answer this, you must know how to read or tell time. I'm sure you do. The typical format of time is the 12-hour format. That is 12 hours in the morning and 12 hours in the afternoon. You just simply have to count from 10 in the morning, until you reach 2 in the afternoon. That would be 11, 12, 1 and 2. You passed 4 numbers in the clock. Therefore, her flight took 4 hours.