a) [tex] \frac{3 \sqrt{8} + 3 \sqrt{8} }{2} = \frac{6 \sqrt{2} + 6 \sqrt{2} }{2} = \frac{12 \sqrt{2} }{2} = 6 \sqrt{2} = 6[/tex]
b) [tex] \frac{ \sqrt{240} + 9 \sqrt{15} }{2} = \frac{4 \sqrt{15} + 9 \sqrt{15} }{2} = \frac{12 \sqrt{5} + 27 \sqrt{5} }{2} = \frac{39 \sqrt{5} }{2} [/tex]