Сравнение значений выражений

1. а) Сравним $$3,6 \cdot 6,8$$ и $$105 : \frac{21}{6}$$
   $$3,6 \cdot 6,8 = 24,48$$
   $$105 : \frac{21}{6} = 105 \cdot \frac{6}{21} = \frac{105 \cdot 6}{21} = \frac{630}{21} = 30$$
   $$24,48 < 30$$
   Значит, $$3,6 \cdot 6,8 < 105 : \frac{21}{6}$$
2. б) Сравним $$13 - 2\frac{2}{3}$$ и $$12 - 1\frac{3}{4}$$
   $$13 - 2\frac{2}{3} = 13 - \frac{8}{3} = \frac{39}{3} - \frac{8}{3} = \frac{31}{3} = 10\frac{1}{3}$$
   $$12 - 1\frac{3}{4} = 12 - \frac{7}{4} = \frac{48}{4} - \frac{7}{4} = \frac{41}{4} = 10\frac{1}{4}$$
   $$10\frac{1}{3} > 10\frac{1}{4}$$
   Значит, $$13 - 2\frac{2}{3} > 12 - 1\frac{3}{4}$$