2- 3 1/7×(2- 1 9/11): 8/21 2 1/3 +4,1: (2 7/15 - 5/12)×5/6 4 5/12 - 1 1/12 : (2 1/6 + 8/15)× 1 4/5 ( 10 )

▪2 - 3 1/7×(2- 1 9/11):8/21 = 2 - 3 1/7 × 2/11 ÷ 8/21 = 2 - 4/7 ÷ 8/21 = 2 - 1,5 = 0,5

1) 2- 1 9/11 = 1 11/11 - 1 9/11 = 2/11
2) 3 1/7 × 2/11 = 22/7 × 2/11 = (22×2)/(7×11) = (2×2)/7 = 4/7
3) 4/7 ÷ 8/21 = 4/7 × 21/8 = (4×21)/(7×8) = 3/2 = 1 1/2 = 1,5
4) 2 - 1,5 = 0,5

▪2 1/3 +4,1:(2 7/15 - 5/12)×5/6 = 2 1/3 + 4,1 ÷ 2 1/20 × 5/6 = 2 1/3 + 2 × 5/6 = 2 1/3 + 1 2/3 = 4

1) 2 7/15 - 5/12 = 2 28/60 - 25/60 = 2 3/60 = 2 целых 1/20
2) 4,1 ÷ 2 1/20 = 41/10 ÷ 41/20 = (41×20)/(10×41) = 2
3) 2 × 5/6 = 5/3 = 1 целая 2/3
4) 2 1/3 + 1 2/3 = 3 целых 3/3 = 4

▪4 5/12 - 1 1/12 : (2 1/6 + 8/15)× 1 4/5 = 4 5/12 - 1 1/12 : 2,7 × 1 4/5 = 4 5/12 - 65/162 × 1 4/5 = 4 5/12 - 13/18 = 3 целых 25/36;

1) 2 1/6 + 8/15 = 2 5/30 + 16/30 = 2 21/30 = 2 7/10 = 2,7
2) 1 1/12 : 2,7 = 13/12 × 10/27 = (13×10)/(12×27) = (13×5)/(6×27) = 65/162
3) 65/162 × 1 4/5 = 65/162 × 9/5 = (65×9)/(162×5) = 13/18
4) 4 5/12 - 13/18 = 4 15/36 - 26/36 = 4 - 11/36 = 3 целых 25/36