Vani is sixth from the front end of a line and Swathi is ninth from the back end of the line of girls. If there are seven girls between Vani and Swathi, how many girls are there in the line?

To calculate the total number of girls in the straight queue line, we sum the distinct segments:
$$\text{Total}=\text{Position of Vani from front}+\text{Girls between them}+\text{Position of Swathi from back}$$

Given:

* Position of Vani from front = $6$
* Position of Swathi from back = $9$
* Girls between Vani and Swathi = $7$

$$\text{Total}=6+7+9=22$$

There are $22$ girls in the line.