3 4 a) 5 1,8⋅11:0,07 5:0,49⋅25;

a) Выполним действия:

1) $$1\frac{1}{5} = \frac{1 \cdot 5 + 1}{5} = \frac{6}{5} = 1,2$$

2) $$1,8 \cdot 1,2 = 2,16$$

3) $$\frac{3}{4} \cdot 2,16 = 1,62$$

4) $$0,07 = \frac{7}{100}$$

5) $$1,62 : \frac{7}{100} = 1,62 \cdot \frac{100}{7} = \frac{162}{7} = 23\frac{1}{7}$$

6) $$25\frac{5}{8} = \frac{25 \cdot 8 + 5}{8} = \frac{205}{8}$$

7) $$0,49 = \frac{49}{100}$$

8) $$\frac{1}{5} : \frac{49}{100} = \frac{1}{5} \cdot \frac{100}{49} = \frac{20}{49}$$

9) $$\frac{20}{49} \cdot \frac{205}{8} = \frac{5}{49} \cdot \frac{205}{2} = \frac{1025}{98} = 10\frac{45}{98}$$

10) $$23\frac{1}{7} : 10\frac{45}{98} = \frac{162}{7} : \frac{1025}{98} = \frac{162}{7} \cdot \frac{98}{1025} = \frac{162}{1} \cdot \frac{14}{1025} = \frac{2268}{1025} = 2\frac{218}{1025}$$

Ответ: $$2\frac{218}{1025}$$