1) (2 7/30-3 1/5*7/12) * 7 1/2

2) (6 3/8-5 7/12) * 5 1/7-6/7

3) 7 * (1/12+1/18) * (1 3/5-4/7)

А) (2 7/30-3 1/5*7/12) * 7 1/2 = 2 43/72

1) 3 1/5*7/12=16/5*7/12=28/15=1 13/15

2) 2 7/30-1 13/15=1 + (7/30-13*2/30) = 1-19/30=11/30

3) 11/30*7 1/12=11/30*85/12=187/72=2 43/72

б) (6 3/8-5 7/12) * 5 1/7-6/7 = - 1 13/14

1) 6 3/8-5 7/12=1 + (3/8-7/12) = 1 = (3*3/24-7*2/24) = 1 + (-5/24) = 19/24

2) - 19/24*5 1/7=-19/24*36/7=57/14=4 1/14

3) - 4 1/14-6/7=-1 + (-1/14-6*2/14) = - 1-13/14=-1 13/14

в) 7 * (1/12+1/18) * (1 3/5-4/7) = 1

1) 1/12+1/18=1*3/36+1*2/36=5/36

2) 7*5/36=35/36

3) 1 3/5-4/7=1 + (3/5-4/7) = 1 + (3*7/35-4*5/35) = 1+1/35=1 1/35=36/35

4) 35/36*36/35=1