$\sqrt{98} - \sqrt{50} + \sqrt{32} = \sqrt{49 * 2} - \sqrt{25 * 2} + \sqrt{16 * 2} = 7\sqrt{2} - 5\sqrt{2} + 4\sqrt{2} = 6\sqrt{2}$

$3\sqrt{8} + \sqrt{128} - \frac{1}{3}\sqrt{162} = 3\sqrt{4 * 2} + \sqrt{64 * 2} - \frac{1}{3}\sqrt{81 * 2} = 3 * 2\sqrt{2} + 8\sqrt{2} - \frac{1}{3} * 9\sqrt{2} = 6\sqrt{2} + 8\sqrt{2} - 3\sqrt{2} = 11\sqrt{2}$

$0,7\sqrt{300} - 7\sqrt{\frac{3}{49}} + \frac{2}{3}\sqrt{108} = 0,7\sqrt{100 * 3} - 7\sqrt{\frac{1}{49} * 3} + \frac{2}{3}\sqrt{36 * 3} = 0,7 * 10\sqrt{3} - 7 * \frac{1}{7}\sqrt{3} + \frac{2}{3} * 6\sqrt{3} = 7\sqrt{3} - \sqrt{3} + 2 * 2\sqrt{3} = 6\sqrt{3} + 4\sqrt{3} = 10\sqrt{3}$

$\sqrt{5a} - 2\sqrt{20a} + 3\sqrt{80a} = \sqrt{5a} - 2\sqrt{4 * 5a} + 3\sqrt{16 * 5a} = \sqrt{5a} - 2 * 2\sqrt{5a} + 3 * 4\sqrt{5a} = \sqrt{5a} - 4\sqrt{5a} + 12\sqrt{5a} = 9\sqrt{5a}$

$\sqrt{a^3b} - \frac{2}{a}\sqrt{a^5b} = \sqrt{a^2 * ab} - \frac{2}{a}\sqrt{a^4 * ab} = a\sqrt{ab} - \frac{2}{a} * a^2\sqrt{ab} = a\sqrt{ab} - 2a\sqrt{ab} = -a\sqrt{ab}$, если a > 0

$\sqrt{c^5} + 4c\sqrt{c^3} - 5c^2\sqrt{c} = \sqrt{c^4 * c} + 4c\sqrt{c^2 * c} - 5c^2\sqrt{c} = c^2\sqrt{c} + 4c * c\sqrt{c} - 5c^2\sqrt{c} = c^2\sqrt{c} + 4c^2\sqrt{c} - 5c^2\sqrt{c} = 0$