1) 5 ⋅ 3/26; 2) 5/8 ⋅ 4; 3) 9/28 ⋅ 56; 4) 6 3/7 ⋅ 3/8; 5) 5 1/7 ⋅ 1 8/27; 6) 1 8/9 ⋅ 1 2/3.

1) $$ 5 \cdot \frac{3}{26} = \frac{5 \cdot 3}{26} = \frac{15}{26} $$

2) $$ \frac{5}{8} \cdot 4 = \frac{5 \cdot 4}{8} = \frac{5 \cdot 4}{2 \cdot 4} = \frac{5}{2} = 2 \frac{1}{2} $$

3) $$ \frac{9}{28} \cdot 56 = \frac{9 \cdot 56}{28} = \frac{9 \cdot 2 \cdot 28}{28} = 9 \cdot 2 = 18 $$

4) $$ 6 \frac{3}{7} \cdot \frac{3}{8} = \frac{6 \cdot 7 + 3}{7} \cdot \frac{3}{8} = \frac{45}{7} \cdot \frac{3}{8} = \frac{45 \cdot 3}{7 \cdot 8} = \frac{135}{56} = 2 \frac{23}{56} $$

5) $$ 5 \frac{1}{7} \cdot 1 \frac{8}{27} = \frac{5 \cdot 7 + 1}{7} \cdot \frac{1 \cdot 27 + 8}{27} = \frac{36}{7} \cdot \frac{35}{27} = \frac{36 \cdot 35}{7 \cdot 27} = \frac{4 \cdot 9 \cdot 5 \cdot 7}{7 \cdot 3 \cdot 9} = \frac{4 \cdot 5}{3} = \frac{20}{3} = 6 \frac{2}{3} $$

6) $$ 1 \frac{8}{9} \cdot 1 \frac{2}{3} = \frac{1 \cdot 9 + 8}{9} \cdot \frac{1 \cdot 3 + 2}{3} = \frac{17}{9} \cdot \frac{5}{3} = \frac{17 \cdot 5}{9 \cdot 3} = \frac{85}{27} = 3 \frac{4}{27} $$

Ответ: 1) 15/26; 2) 2 1/2; 3) 18; 4) 2 23/56; 5) 6 2/3; 6) 3 4/27