8) 12 - 6

1. Convert mixed numbers to improper fractions: $$12\frac{3}{4} = \frac{51}{4}$$, $$6\frac{7}{8} = \frac{55}{8}$$.
2. Find a common denominator (8): $$\frac{51}{4} = \frac{102}{8}$$.
3. Subtract the fractions: $$\frac{102}{8} - \frac{55}{8} = \frac{47}{8} = 5\frac{7}{8}$$.