1. Вычислить: а) 5/6 + 7/12 ⋅ 7/2 ; б) (7/15 - 1/12) ⋅ 20/3 ; в) 2,6-8,4/2,5 ; г) -3,25 ⋅ (-4,2 + 3,6).

а) \[\frac{5}{6} + \frac{7}{12} \cdot \frac{7}{2} = \frac{5}{6} + \frac{49}{24} = \frac{20}{24} + \frac{49}{24} = \frac{69}{24} = \frac{23}{8} = 2.875\]

б) \[\left(\frac{7}{15} - \frac{1}{12}\right) \cdot \frac{20}{3} = \left(\frac{28}{60} - \frac{5}{60}\right) \cdot \frac{20}{3} = \frac{23}{60} \cdot \frac{20}{3} = \frac{23}{9} = 2.\overline{5}\]

в) \[\frac{2.6 - 8.4}{2.5} = \frac{-5.8}{2.5} = -2.32\]

г) \[-3.25 \cdot (-4.2 + 3.6) = -3.25 \cdot (-0.6) = 1.95\]