к) $$5\frac{3}{4} \cdot 1\frac{1}{7} = \frac{23}{4} \cdot \frac{8}{7} = \frac{23 \cdot 8}{4 \cdot 7} = \frac{23 \cdot 2}{1 \cdot 7} = \frac{46}{7} = 6\frac{4}{7}$$
Ответ: $$6\frac{4}{7}$$