[tex]a) \: \: \: a = ( \frac{20}{ \sqrt{1800} } - \frac{3}{ \sqrt{72} } ) \div \frac{1}{84} \\ a = ( \frac{20}{30 \sqrt{2} } - \frac{3}{6 \sqrt{2} } ) \times \frac{84}{1} \\ a = \frac{4 - 3}{6 \sqrt{2} } \times \frac{84}{1} \\ a = \frac{84}{6 \sqrt{2} } \\ a = \frac{84 \sqrt{2} }{12} \\ a = 7 \sqrt{2} \\ \\ b) \: \: \: b = ( \sqrt{3} - 3) {}^{2} - \sqrt{( \sqrt{3} - 2) {}^{2} } + \sqrt{75} \\ b = 3 - 6 \sqrt{3} + 9 - | \sqrt{3} - 2 | + 5 \sqrt{3} \\ b = 12 - 6 \sqrt{3} + 6 \sqrt{3} - 2 \\ b = 10 \\ a = 7 \sqrt{2} \\ \sqrt{98} < \sqrt{100} = > a < b[/tex]
