<span>а)(3/4+1/6)+7/12=3/4+(1/6+7/12);
</span>(3/4+1/6)+7/12 =
![( \frac{3*3}{3*4} + \frac{2*1}{2*6} )+ \frac{7}{12} = ( \frac{9}{12} + \frac{2}{12} )+ \frac{7}{12} = \frac{11}{12} + \frac{7}{12} = \frac{11+7}{12} = \frac{18}{12} = \frac{3}{2} =1 \frac{1}{2}](https://tex.z-dn.net/?f=%28+%5Cfrac%7B3%2A3%7D%7B3%2A4%7D+%2B++%5Cfrac%7B2%2A1%7D%7B2%2A6%7D++%29%2B++%5Cfrac%7B7%7D%7B12%7D++%3D+%28+%5Cfrac%7B9%7D%7B12%7D+%2B+%5Cfrac%7B2%7D%7B12%7D+%29%2B+%5Cfrac%7B7%7D%7B12%7D+%3D++%5Cfrac%7B11%7D%7B12%7D+%2B+%5Cfrac%7B7%7D%7B12%7D+%3D+%5Cfrac%7B11%2B7%7D%7B12%7D+%3D+%5Cfrac%7B18%7D%7B12%7D+%3D+%5Cfrac%7B3%7D%7B2%7D+%3D1+%5Cfrac%7B1%7D%7B2%7D+)
3/4+(1/6+7/12) =
![\frac{3}{4} + ( \frac{2*1}{2*6} + \frac{7}{12})= \frac{3}{4} +( \frac{2}{12} + \frac{7}{12} ) = \frac{3}{4} + \frac{9}{12} = \frac{3*3}{3*4} + \frac{9}{12} = \frac{9}{12} + \frac{9}{12} = \frac{18}{12}](https://tex.z-dn.net/?f=+%5Cfrac%7B3%7D%7B4%7D+%2B+%28+%5Cfrac%7B2%2A1%7D%7B2%2A6%7D+%2B+%5Cfrac%7B7%7D%7B12%7D%29%3D++%5Cfrac%7B3%7D%7B4%7D++%2B%28+%5Cfrac%7B2%7D%7B12%7D+%2B+%5Cfrac%7B7%7D%7B12%7D+%29+%3D++%5Cfrac%7B3%7D%7B4%7D+%2B+%5Cfrac%7B9%7D%7B12%7D+%3D+%5Cfrac%7B3%2A3%7D%7B3%2A4%7D+%2B+%5Cfrac%7B9%7D%7B12%7D+%3D+%5Cfrac%7B9%7D%7B12%7D+%2B+%5Cfrac%7B9%7D%7B12%7D+%3D+%5Cfrac%7B18%7D%7B12%7D)
=
![1 \frac{1}{2}](https://tex.z-dn.net/?f=1+%5Cfrac%7B1%7D%7B2%7D+)
![1 \frac{1}{2} =1 \frac{1}{2}](https://tex.z-dn.net/?f=1+%5Cfrac%7B1%7D%7B2%7D+%3D1+%5Cfrac%7B1%7D%7B2%7D+)
<span>
б)7/15+(2/9+5/6)=(7/15+2/9)+5/6.
</span>7/15+(2/9+5/6)=
![\frac{7}{15} +( \frac{2*2}{2*9} + \frac{3*5}{3*6} ) = \frac{7}{15} +( \frac{4}{18} + \frac{15}{18} ) = \frac{7}{15} + \frac{19}{18} = \frac{6*7}{6*15} + \frac{5*19}{5*18} = \frac{42}{90} + \frac{95}{90} ](https://tex.z-dn.net/?f=+%5Cfrac%7B7%7D%7B15%7D+%2B%28+%5Cfrac%7B2%2A2%7D%7B2%2A9%7D+%2B+%5Cfrac%7B3%2A5%7D%7B3%2A6%7D+%29+%3D++%5Cfrac%7B7%7D%7B15%7D+%2B%28+%5Cfrac%7B4%7D%7B18%7D+%2B+%5Cfrac%7B15%7D%7B18%7D+%29+%3D++%5Cfrac%7B7%7D%7B15%7D+%2B+%5Cfrac%7B19%7D%7B18%7D+%3D+%5Cfrac%7B6%2A7%7D%7B6%2A15%7D+%2B+%5Cfrac%7B5%2A19%7D%7B5%2A18%7D+%3D+%5Cfrac%7B42%7D%7B90%7D+%2B+%5Cfrac%7B95%7D%7B90%7D+%0A)
=
![\frac{137}{90} =1 \frac{47}{90}](https://tex.z-dn.net/?f=+%5Cfrac%7B137%7D%7B90%7D+%3D1+%5Cfrac%7B47%7D%7B90%7D+)
(7/15+2/9)+5/6 =
![( \frac{3*7}{3*15} + \frac{5*2}{5*9} )+ \frac{5}{6} =( \frac{21}{45} + \frac{10}{45} )+ \frac{5}{6} = \frac{31}{45} + \frac{5}{6} = \frac{2*31}{2*45} + \frac{15*5}{15*6} = \frac{62}{90} + \frac{75}{90}](https://tex.z-dn.net/?f=%28+%5Cfrac%7B3%2A7%7D%7B3%2A15%7D+%2B+%5Cfrac%7B5%2A2%7D%7B5%2A9%7D+%29%2B+%5Cfrac%7B5%7D%7B6%7D+%3D%28+%5Cfrac%7B21%7D%7B45%7D+%2B+%5Cfrac%7B10%7D%7B45%7D+%29%2B+%5Cfrac%7B5%7D%7B6%7D+%3D+%5Cfrac%7B31%7D%7B45%7D+%2B+%5Cfrac%7B5%7D%7B6%7D+%3D+%5Cfrac%7B2%2A31%7D%7B2%2A45%7D+%2B+%5Cfrac%7B15%2A5%7D%7B15%2A6%7D+%3D+%5Cfrac%7B62%7D%7B90%7D+%2B+%5Cfrac%7B75%7D%7B90%7D+)
=
![\frac{137}{90} =1 \frac{47}{90}](https://tex.z-dn.net/?f=+%5Cfrac%7B137%7D%7B90%7D+%3D1+%5Cfrac%7B47%7D%7B90%7D+)
![1 \frac{47}{90} =1 \frac{47}{90}](https://tex.z-dn.net/?f=1+%5Cfrac%7B47%7D%7B90%7D+%3D1+%5Cfrac%7B47%7D%7B90%7D+)
Необходимо 40 дней перевести сначала в часы, а потом в минуты и умножить
40 дней=960 часов=57600 минут
1) 25* 57600=1440000 минут
Удачи))