2. Найдите значение выражения: a) -29 + 12 + (-40) + (-31) + 38; б) -6/13 ⋅ 4 5/6 ⋅ 13/6; в) -11/15 ⋅ 4,2 - 4,2 ⋅ 4/15.

Решение: a) $$-29 + 12 + (-40) + (-31) + 38 = -29 + 12 - 40 - 31 + 38 = (12+38) - (29+40+31) = 50 - 100 = -50$$ б) $$-\frac{6}{13} \cdot 4\frac{5}{6} \cdot \frac{13}{6} = -\frac{6}{13} \cdot \frac{29}{6} \cdot \frac{13}{6} = -\frac{6 \cdot 29 \cdot 13}{13 \cdot 6 \cdot 6} = -\frac{29}{6} = -4\frac{5}{6}$$ в) $$-\frac{11}{15} \cdot 4.2 - 4.2 \cdot \frac{4}{15} = 4.2 \cdot (-\frac{11}{15} - \frac{4}{15}) = 4.2 \cdot (-\frac{15}{15}) = 4.2 \cdot (-1) = -4.2$$ Ответ: a) -50 б) -4 5/6 в) -4.2