1) $\sqrt{54} - \sqrt{128}$

2) $12\sqrt{2} + 20\sqrt{54} - \sqrt{128}$

3) $9\sqrt{2} - 6\sqrt{18} + 4\sqrt{50}$

4) $(2\sqrt{3} + 3\sqrt{2})(2\sqrt{3} - 3\sqrt{2})$

5) $(3\sqrt{45}) \div \sqrt{5}$

6) $(\sqrt{20} + \sqrt{45}) \div \sqrt{5}$

7) $3(1 + \sqrt{2}) - 5(1 - \sqrt{2})$