Tính giá trị các biểu thức sau

$a) \frac{\sqrt{7}-5}{2}-\frac{6-2\sqrt{7}}{4}+\frac{6}{\sqrt{7}-2}-\frac{5}{4+\sqrt{7}}$

$b) \frac{2}{\sqrt{6}-2}+\frac{2}{\sqrt{6}+2}+\frac{5}{\sqrt{6}}$
 
$c) \left(\frac{\sqrt{6}-\sqrt{2}}{1-\sqrt{3}}-\frac{5}{\sqrt{5}}\right):\frac{1}{\sqrt{5}-\sqrt{2}}$

$d) \frac{1}{\sqrt{3}}+\frac{1}{3\sqrt{3}}+\frac{1}{\sqrt{3}}\sqrt{\frac{5}{12}-\frac{1}{16}}$