By how much does 67/8 exceed 6/78 = ?

Answer: Option B

$$\begin{array}{rl}& \frac{6}{7/8}-\frac{6/7}{8}\\ & =6\times \frac{8}{7}-\frac{6}{7}\times \frac{1}{8}\\ & =\frac{48}{7}-\frac{6}{56}\\ & =\frac{384-6}{56}\\ & =\frac{378}{56}\\ & =\frac{27}{4}\\ & =6\frac{3}{4}\end{array}$$