Answer:
21
Step-by-step explanation:
mode is the value that occurs frequently
data
15, 21, 26, 25, 21, 23, 28, 21, 25, 23
sort from the smallest
15, 21, 21, 21, 23, 23, 25, 25, 26, 28
15 = 1
21 = 3
26 = 1
25 = 2
23 = 2
28 = 1
the mode is 21 (appear 3 times)
