Find the value of x in the diagram. Find the median.

The arrows indicate two parallel lines.

This divides angle $x$ into two parts, let's call them $\alpha$ and $\beta$.

The angle $35^\circ$ is an alternate interior angle to the upper part of $x$. So, $\alpha = 35^\circ$.
The angle $130^\circ$ is an exterior angle. The interior angle adjacent to it is $180^\circ - 130^\circ = 50^\circ$. This $50^\circ$ angle is an alternate interior angle to the lower part of $x$. So, $\beta = 50^\circ$.

The final answer is $\boxed{\text{C. } 85^\circ}$.

48. Find the median.

Since the total number of students is even ($N=30$), the median is the average of the $\frac{N}{2}$-th and $(\frac{N}{2} + 1)$-th values.

So, we need the 15th and 16th values.

• For 1 subject: 2 students (CF = 2)
• For 2 subjects: 1 student (CF = 2 + 1 = 3)
• For 3 subjects: 4 students (CF = 3 + 4 = 7)
• For 4 subjects: 3 students (CF = 7 + 3 = 10)
• For 5 subjects: 8 students (CF = 10 + 8 = 18) The 15th and 16th values both fall within the "5 subjects" category, as the cumulative frequency reaches 18 at this point.

The final answer is $\boxed{\text{B. } 5}$.

49. Calculate the mean of the distribution.

$\text{Mean} = \frac{\sum (x \cdot f)}{\sum f}$.
We already found $\sum f = 30$ in question 48.

The final answer is $\boxed{\text{B. } 5}$.