30. Вычислите: 1) 25,2 : 3 1/2 + (6 - 4 1/3) * 0,6; 2) (7 - 1 5/12) : 6,7 + (5,75 - 3 1/6) : 15,5.

Решение:

1) \( 25,2 : 3\frac{1}{2} + (6 - 4\frac{1}{3}) \cdot 0,6 \)

1. \( 3\frac{1}{2} = \frac{7}{2} = 3,5 \)
2. \( 6 - 4\frac{1}{3} = 6 - \frac{13}{3} = \frac{18-13}{3} = \frac{5}{3} \)
3. \( 25,2 : 3,5 = 252 : 35 = 7,2 \)
4. \( \frac{5}{3} \cdot 0,6 = \frac{5}{3} \cdot \frac{3}{5} = 1 \)
5. \( 7,2 + 1 = 8,2 \)

2) \( (7 - 1\frac{5}{12}) : 6,7 + (5,75 - 3\frac{1}{6}) : 15,5 \)

1. \( 7 - 1\frac{5}{12} = 7 - \frac{17}{12} = \frac{84-17}{12} = \frac{67}{12} \)
2. \( 5,75 - 3\frac{1}{6} = 5\frac{3}{4} - 3\frac{1}{6} = \frac{23}{4} - \frac{19}{6} = \frac{69-38}{12} = \frac{31}{12} \)
3. \( \frac{67}{12} : 6,7 = \frac{67}{12} : \frac{67}{10} = \frac{67}{12} \cdot \frac{10}{67} = \frac{10}{12} = \frac{5}{6} \)
4. \( \frac{31}{12} : 15,5 = \frac{31}{12} : \frac{31}{2} = \frac{31}{12} \cdot \frac{2}{31} = \frac{2}{12} = \frac{1}{6} \)
5. \( \frac{5}{6} + \frac{1}{6} = \frac{6}{6} = 1 \)

Ответ: 1) 8,2; 2) 1.