Solve in English

The highest value in the $f_i$ column is 7.

The $x_i$ value corresponding to the frequency of 7 is 7.
The mode is $\boxed{7}$.

The mean ($\bar{x}$) is given by the sum of $x_i f_i$ divided by the sum of $f_i$.

From the table, $\sum x_i f_i = 138$ and $\sum f_i = 20$.

The mean is $\boxed{6.9}$.

The total number of observations is $N = \sum f_i = 20$. Since $N$ is even, the median is the average of the $\frac{N}{2}$-th and $(\frac{N}{2}+1)$-th values.

We need the 10th and 11th values.

Looking at the CF column:

• The 10th value falls within the range where CF is 15, which corresponds to $x_i = 7$.
• The 11th value also falls within this range, corresponding to $x_i = 7$. The 10th value is 7. The 11th value is 7.

The median is $\boxed{7}$.