Answer
See below.
Work Step by Step
The mean of $n$ numbers is the sum of the numbers divided by $n$. The median of $n$ is the middle number of the numbers when they are in order (and the mean of the middle $2$ numbers if $n$ is even). The mode of $n$ numbers is the number or numbers that appear(s) most frequently.
Hence here the mean: $\frac{2+6+6+16+19+20+20+21+22+25+26+30}{12}=17.75$.
The median is the average of the middle two in the sequence $2, 6, 6, 16, 19, 20, 20, 21, 22, 25, 26, 30$, which is: $(20+20)/2=20$.
The modes are $6,20$.
