Giải phương trình sau:
a) ($2\sqrt{6}$ -$4\sqrt{3}$ +$5\sqrt{2}$ -$\frac{1}{4}\sqrt{8}$ ).$3\sqrt{6}$
b) ($\sqrt{\frac{1}{7}}$ - $\sqrt{ \frac{16}{7}} $ +$\sqrt{7}$ ):$\sqrt{7}$
c) ($\sqrt{325}$- $\sqrt{117}$ +$2\sqrt{208}$ ):$\sqrt{13}$
d) ($\frac{1}{3}\sqrt{\frac{1}{2} }$ -$\frac{2}{3}\sqrt{\frac{3}{2} }$ +$\frac{2}{7}\sqrt{\frac{1}{6} }$ ):($\frac{2}{7}\sqrt{\frac{1}{8} }$)