а) \(\frac{1}{2}\sqrt{12} - 2\sqrt{27} + \sqrt{75} = \frac{1}{2}\sqrt{4 \cdot 3} - 2\sqrt{9 \cdot 3} + \sqrt{25 \cdot 3} = \frac{1}{2} \cdot 2\sqrt{3} - 2 \cdot 3\sqrt{3} + 5\sqrt{3} = \sqrt{3} - 6\sqrt{3} + 5\sqrt{3} = (1 - 6 + 5)\sqrt{3} = 0\sqrt{3} = 0\)
Ответ: 0.