[tex]\text{Area of triangle} = \dfrac 12 \times PQ \times QR \times \sin \angle PQR \\\\\\\implies 273= \dfrac 12 \times 12.8 \times QR \times \sin 107^{\circ}\\\\\implies 273 = 6.4 \sin 107^{\circ} \times QR\\\\\\\implies QR = \dfrac{273}{6.4 \sin 107^{\circ}} = 44. 606~~ \text{cm}[/tex]
