\(PR^2 = PQ^2 + RQ^2 - 2(PQ)(RQ)cos Q\) \(\implies cos Q = \frac{PQ^2 + RQ^2 - PR^2}{2(PQ)(RQ)}\) \(\implies cos Q = \frac{8^2 + 5^2 - 7^2}{2\times8\times5}\) \(\implies cos Q = \frac{64 + 25 - 49}{80}\) \(\implies cos Q = \frac{40}{80} = 0.5\) \(\implies Q = cos^{-1} (0.5) = 60^0\) \(\therefore x = 60^0\)