178. Выполните вычитание: 1) 16,7 – (-8,9); 2) 7,2 – 8,9; 3)0 – 5,7; 4)-13,6 – 14,4; 5)-14,8 – (-8,12); 6) 0 – (-19,3); 7)\frac{7}{24}-(\frac{17}{36}); 8) 2\frac{1}{9}-\frac{2}{3}; 9) 3\frac{1}{5}-(-\frac{4}{7}).

Ответ: 1) 25,6; 2) -1,7; 3) -5,7; 4) -28; 5) -6,68; 6) 19,3; 7) -1/72; 8) 16/9; 9) 132/35

Решение:

1. 16,7 – (-8,9) = 16,7 + 8,9 = 25,6
2. 7,2 – 8,9 = -1,7
3. 0 – 5,7 = -5,7
4. -13,6 – 14,4 = -28
5. -14,8 – (-8,12) = -14,8 + 8,12 = -6,68
6. 0 – (-19,3) = 19,3
7. \[\frac{7}{24} - \frac{17}{36} = \frac{7 \cdot 3}{24 \cdot 3} - \frac{17 \cdot 2}{36 \cdot 2} = \frac{21}{72} - \frac{34}{72} = \frac{21 - 34}{72} = \frac{-13}{72} = -\frac{13}{72}\]
8. \[2\frac{1}{9} - \frac{2}{3} = \frac{19}{9} - \frac{2}{3} = \frac{19}{9} - \frac{2 \cdot 3}{3 \cdot 3} = \frac{19}{9} - \frac{6}{9} = \frac{19 - 6}{9} = \frac{13}{9} = 1\frac{4}{9} = \frac{13}{9}\]
9. \[3\frac{1}{5} - \left(-\frac{4}{7}\right) = \frac{16}{5} + \frac{4}{7} = \frac{16 \cdot 7}{5 \cdot 7} + \frac{4 \cdot 5}{7 \cdot 5} = \frac{112}{35} + \frac{20}{35} = \frac{112 + 20}{35} = \frac{132}{35} = 3\frac{27}{35} = \frac{132}{35}\]

Ответ: 1) 25,6; 2) -1,7; 3) -5,7; 4) -28; 5) -6,68; 6) 19,3; 7) -1/72; 8) 16/9; 9) 132/35