二錄二二号:卡內 이음유 ==2 613 3 1127=2.8+4=168+4=00 2号=2.5+4=10+4=17 二18+二路5=17 2120.14- 8 904 trob y=280 40 511 1 885:40-7=4 40:401

Разбираемся с решениями на фото:

1. \[\frac{1}{4} : \frac{4}{5} = \frac{1}{4} \cdot \frac{5}{4} = \frac{1 \cdot 5}{4 \cdot 4} = \frac{5}{16}\]

2. \[\frac{5}{12} : \frac{8}{9} - \frac{2}{3} : \frac{2}{9} = \frac{5}{12} \cdot \frac{9}{8} - \frac{2}{3} \cdot \frac{9}{2} = \frac{5 \cdot 3}{4 \cdot 8} - \frac{1 \cdot 3}{1 \cdot 1} = \frac{15}{32} - 3 = \frac{15}{32} - \frac{96}{32} = - \frac{81}{32}\]

3. \[(3 \frac{1}{8} - 2 \frac{1}{2} : \frac{2}{5}):1 \frac{1}{5} = (\frac{25}{8} - \frac{5}{2} \cdot \frac{5}{2}) : \frac{6}{5} = (\frac{25}{8} - \frac{25}{4}) : \frac{6}{5} = (\frac{25}{8} - \frac{50}{8}) : \frac{6}{5} = -\frac{25}{8} \cdot \frac{5}{6} = - \frac{125}{48}\]

4. \(2 \frac{4}{8} = 2 \cdot 8 + 4 = 16 + 4 = \frac{20}{8}\)

   \(2 \frac{4}{5} = 2 \cdot 5 + 4 = 10 + 4 = \frac{14}{5}\)

   \(1 \frac{5}{8} = 1 \cdot 8 + 5 = 8 + 5 = \frac{13}{8}\)

5. \[20 \cdot \frac{14}{5} = \frac{280}{5} = 56\]

   Решим деление столбиком:

         7
       -----   
     40|280
       |280
       -----
         0
     

   \[280 : 40 = \frac{280}{40} = \frac{28}{4} = 7 \]