[tex] \frac{12}{ \sqrt{7 + \sqrt{3} } } [/tex]

[tex] = \frac{12 \sqrt{7 + \sqrt{3} } }{ 7 + \sqrt{3} } \\ = \frac{12 \sqrt{7 + \sqrt{3 \times (7 - \sqrt{3)} } } }{46} \\ = \frac{6 \sqrt{7 + \sqrt{3 \times (7 - \sqrt{3)} } } }{23}[/tex]