[tex] \sqrt{75} + \sqrt{108} = a \sqrt{b} [/tex]
[tex] \sqrt{75} = \sqrt{3 \times 5 {}^{2} } = 5 \sqrt{3} [/tex]
[tex] \sqrt{108} = \sqrt{2 {}^{2} + 3 {}^{3} } = 2 \times 3 \sqrt{3} = 6 \sqrt{3} [/tex]
[tex] \sqrt{75} + \sqrt{108} = 5\sqrt{3} + 6 \sqrt{3} = 11 \sqrt{3} [/tex]
[tex]a = 11[/tex]
[tex]b = 3[/tex]