from the question;
we are given the following numbers
[tex]12,\text{ 1 , 15},\text{ 21, 4, 5, 31, }9,\text{ 8, 11}[/tex]
we are to find the range of the numbers
but range is defined as
[tex]\text{Range = Highest value - Lowest value}[/tex]
From the numbers
[tex]\begin{gathered} \text{Highest value = 31 } \\ \text{Lowest value = 1} \end{gathered}[/tex]
Therefore
[tex]\begin{gathered} \text{Range = 31 - 1} \\ \text{Range = 30} \end{gathered}[/tex]
Therefore,
The range of the numbers is 30
