Mode is the value appearing most frequently.
Counting: 4 appears 3 times, 6 appears 3 times, 7 appears 3 times, 9 appears 4 times, 10 appears 2 times, 5 appears 2 times, 3 appears 2 times, 2 appears 1 time.
9 appears 4 times, which is the highest frequency. Mode = 9.