To find the percentage of people between the ages of 21 and 34 who prefer football, we need to consider the number of individuals who prefer football in that age group and divide it by the total number of respondents in that same age group.
From the table, for the 21-34 age group, the number of people who prefer football is 9.
The total number of people in the 21-34 age group is 36.
Now, we can calculate the percentage:
\[ \text{Percentage} = \left( \frac{\text{Number of people who prefer football}}{\text{Total number of people in age group}} \right) \times 100 \]
\[ \text{Percentage} = \left( \frac{9}{36} \right) \times 100 \]
\[ \text{Percentage} = 0.25 \times 100 = 25 \]
Therefore, the percentage of people between the ages of 21 and 34 who prefer football is 25%.