172. Найдите сумму: 1) -6 + (-10); 2) -0,84 + (-0,28); 3) -0,68 + (-1,6); 4) -5 \frac{7}{9} + (-2 \frac{4}{9}); 5) -\frac{2}{9} + (-\frac{1}{12}); 6) -8 \frac{2}{15} + (-7 \frac{1}{18}).

**Решение:** 1) -6 + (-10) = -6 - 10 = -16 2) -0,84 + (-0,28) = -0,84 - 0,28 = -1,12 3) -0,68 + (-1,6) = -0,68 - 1,6 = -2,28 4) -5 \frac{7}{9} + (-2 \frac{4}{9}) = -5 \frac{7}{9} - 2 \frac{4}{9} = -(5 \frac{7}{9} + 2 \frac{4}{9}) = -(7 \frac{11}{9}) = -(7 + 1 \frac{2}{9}) = -8 \frac{2}{9} 5) -\frac{2}{9} + (-\frac{1}{12}) = -\frac{2}{9} - \frac{1}{12} = -(\frac{2}{9} + \frac{1}{12}) = -(\frac{8}{36} + \frac{3}{36}) = -\frac{11}{36} 6) -8 \frac{2}{15} + (-7 \frac{1}{18}) = -8 \frac{2}{15} - 7 \frac{1}{18} = -(8 \frac{2}{15} + 7 \frac{1}{18}) = -(8 \frac{12}{90} + 7 \frac{5}{90}) = -(15 \frac{17}{90}) = -15 \frac{17}{90} **Ответы:** 1) -16 2) -1,12 3) -2,28 4) -8 \frac{2}{9} 5) -\frac{11}{36} 6) -15 \frac{17}{90}