Explanation:
If the figure is triangle then,
Let PR be x
So,
PQ+QR+PR= 180 (Sum of all the angles of the triangle)
Therefore,
6x+25+16-3x+x=180
4x+36=180
4x= 180/36
x= 144/4
X= 36
NOW,
PQ= 6x+25
= 6(36)+25
= 216+25 = 241= PQ.
QR = 16-3x
= 16-3(36)
= 16-108
= -92
PR = 36
hope it helps