To find the sum \( p + q \) where \( p \) is positive and \( q \) is negative, you start from the position of \( p \) on the number line and then move to the left by the absolute value of \( q \) (which represents how far you go in the negative direction).
Given this, the correct representation among the options would show:
- Point \( p \) being located positively on the number line.
- An arrow pointing left from \( p \) indicating that you're subtracting the value of \( q \) (moving into the negative).
From the descriptions provided, the third option mentions that point \( p \) is marked on the seventh interval from the left (indicating it's positive), and there is a leftward arrow labeled with the absolute value of \( q \) moving from \( p \) to the second interval from the left (which accounts for moving into the negative).
This aligns perfectly with the operation of adding a negative number.
Therefore, the correct number line showing how to find the sum \( p + q \) is the third option.