\(=\dfrac{12+3\sqrt{3}+4\sqrt{5}+\sqrt{15}+12-3\sqrt{3}-4\sqrt{5}+\sqrt{15}}{13}\)
\(=\dfrac{24+2\sqrt{15}}{13}\)
\(=\dfrac{\left(3+\sqrt{5}\right)\left(4+\sqrt{3}\right)+\left(3-\sqrt{5}\right)\left(4-\sqrt{3}\right)}{13}\\ =\dfrac{12+3\sqrt{3}+4\sqrt{5}+\sqrt{15}+12-3\sqrt{3}-4\sqrt{5}+\sqrt{15}}{13}\\ =\dfrac{24+2\sqrt{15}}{13}\)