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Номера 420,421,424.

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Прикрепленные изображения:

№420.
а) 2/9 : 5 = 2/9 : 5/1 = 2/9 * 1/5 = 2/45
б) 18/23 : 2 = 18/23 : 2/1 = 18/23 * 1/2 = 9/23
в) 22/7 : 8 = 22/7 : 8/1 = 22/7 * 1/8 = 22/56 = 11/28
г) 24/35 : 16 = 24/35 : 16/1 = 24/35 * 1/16 = 3/70
д) с/d : n = c/d : n/1 = c/d * 1/n = c/dn

№421.
а) 1 5/11 : 8/17 = 16/11 : 8/17 = 16/11 * 17/8 = 34/11 = 3 1/11
б) 18/25 : 2 2/5 = 18/25 : 12/5 = 18/25 * 5/12 = 3/10
в) 5 1/3 : 6 2/3 = 16/3 : 20/3 = 16/3 * 3/20 = 16/20 = 4/5
г) 7 5/7 : 4 2/7 = 54/7 : 30/7 = 54/7 * 7/30 = 54/30 = 1 24/30 = 1 4/5
д) 56 : 4 4/5 = 56/1 : 24/5 = 56/1 * 5/24 = 35/3 = 11 2/3
е) 12 3/5 : 9 = 63/5 : 9/1 = 63/5 * 1/9 = 7/5 = 1 2/5
ж) 27 6/7 : 3 = 195/7 : 3/1 = 195/7 * 1/3 = 65/7 =
9 2/7
з) 40 15/17 : 5 = 695/17 : 5/1 = 695/17 * 1/5 = 139/17 = 8 3/17
и) 9 1/8 : 9 1/8 = 1
к) 0 : 3 4/13 = 0

№424.
1) 2 1/4 8 3/4 : 6 2/3 = 2 1/4 35/4 : 20/3 =
2 1/4 35/4 * 3/20 = 2 1/4 (7*3)/(4*4) = 2 1/4 21/16 = 2 1/4 1 5/16 = 2 4/16 1 5/16 = 3 9/16

2) (1 1/3)^2 * (1 1/2)^3 : 2 2/5 = (4/3)^2 * (3/2)^3 : 2 2/5 = 16/9 * 27/8 : 12/5 = 6/2 : 12/5 = 6/2 * 5/12 = 5/4 = 1 1/4

3) (1 1/2 - 3/4) * (5 - 1 2/3) : 3 1/8
Решаем по действиям:
1) 1 1/2 - 3/4 = 3/2 - 3/4 = 6/4 - 3/4 = 3/4
2) 5 - 1 2/3 = 4 3/3 - 1 2/3 = 3 1/3
3) 3/4 * 3 1/3 = 3/4 * 10/3 = 10/4
4) 10/4 : 3 1/8 = 10/4 : 25/8 = 10/4 * 8/25 = 2/10
Ответ: 2/10