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

Answer: Option B

$$\begin{array}{rl}& \frac{6}{\frac{7}{8}}=\frac{6\times 8}{7}=\frac{48}{7}\\ & \frac{\frac{6}{7}}{8}=\frac{6}{7\times 8}=\frac{6}{56}=\frac{3}{28}\\ & \text{Difference - }\\ & =\frac{48}{7}-\frac{3}{28}\\ & =\frac{192-3}{28}\\ & =\frac{189}{28}\\ & =\frac{27}{4}\\ & =6\frac{3}{4}\end{array}$$