Mean : 16
Median : 17
Mode : 18
Explanation :
Mean :
8+9+12+12+13+13+13+15+16+16+16+17+17+18+18+18+18+18+19+19+19+19+20+20 = 383
383 divided by 24 = 15.95
Rounded : 16
Median :
8+9+12+12+13+13+13+15+16+16+16+17+17+18+18+18+18+18+19+19+19+19+20+20
There are 24 numbers here, the two middle numbers are 17 and 17.
17+17 = 34
34 divided by 2 = 17
Mode :
8+9+12+12+13+13+13+15+16+16+16+17+17+18+18+18+18+18+19+19+19+19+20+20
We see here 18 is repeated 5x, thus making it the number repeated the most.