[题目] dfrac (6)(7)div 2-|||-dfrac (1)(2)times dfrac (5)(8)times dfrac (2)(5)-|||-times dfrac (1)(4)div dfrac (3)(2)-|||-dfrac (4)(15)div dfrac (2)(3)-|||-dfrac (5)(12)div dfrac (3)(4)div dfrac (5)(6)-|||-dfrac (5)(6)div dfrac (5)(6)times dfrac (6)(7)

步骤 1：$\dfrac {6}{7}\div 2$
将除法转换为乘法，即乘以2的倒数。
$\dfrac {6}{7}\div 2 = \dfrac {6}{7}\times \dfrac {1}{2}$

步骤 2：$\dfrac {1}{2}\times \dfrac {5}{8}\times \dfrac {2}{5}$
将分数相乘，分子乘分子，分母乘分母。
$\dfrac {1}{2}\times \dfrac {5}{8}\times \dfrac {2}{5} = \dfrac {5}{16}\times \dfrac {2}{5}$

步骤 3：$4\times \dfrac {1}{4}\div \dfrac {3}{2}$
先进行乘法运算，再将除法转换为乘法。
$4\times \dfrac {1}{4}\div \dfrac {3}{2} = 1\div \dfrac {3}{2} = 1\times \dfrac {2}{3}$

步骤 4：$\dfrac {4}{15}\div \dfrac {2}{3}$
将除法转换为乘法，即乘以$\dfrac {2}{3}$的倒数。
$\dfrac {4}{15}\div \dfrac {2}{3} = \dfrac {4}{15}\times \dfrac {3}{2}$

步骤 5：$\dfrac {5}{12}\div \dfrac {3}{4}\div \dfrac {5}{6}$
将除法转换为乘法，即乘以$\dfrac {3}{4}$和$\dfrac {5}{6}$的倒数。
$\dfrac {5}{12}\div \dfrac {3}{4}\div \dfrac {5}{6} = \dfrac {5}{12}\times \dfrac {4}{3}\times \dfrac {6}{5}$

步骤 6：$\dfrac {5}{6}\div \dfrac {5}{6}\times \dfrac {6}{7}$
将除法转换为乘法，即乘以$\dfrac {5}{6}$的倒数。
$\dfrac {5}{6}\div \dfrac {5}{6}\times \dfrac {6}{7} = 1\times \dfrac {6}{7}$