Given:

To find:
The value of QN.
Solution:
From the figure it is clear that, point Q is the intersection point of angle bisectors. So, point Q is the incenter.
...(i) [Incenter is equidistant from each side of triangle]
Using (i), we get




Divide both sides by -3.

Now,




Using (i), we get

Therefore, the value of QN is 17.