The median in a stem-and-leaf diagram is the number that is repeated the most. In this case, the number 78 is repeated 4 times (7 | 8 8 8 8). No other number in the diagram is repeated as much or more than the number 78.
Do not make the mistake of writing the answer as 8 instead of 78.You also want to make sure you don't accidently count 68 which is repeated twice (by looking at the 8's at the end and thinking it's part of the all/rest of the 8's in the diagram).
