4 целых 5,6 - 2 целых 4,9 + 3 целых 1,2 3 целых 11,15-2 целых 3,5+1 целых 9,10 (2 целых3,5+1 целых 7,10+17,20).20 (6 цел. 5,12+2 цел. 2,3-5 цел. 1,12).3,4

№1

4 5/6 - 2 4/9 + 3 1/2 = 5 8/9.

1) 4 5/6 - 2 4/9 = 29/6 - 22/9 = (29 * 3) / (6 * 3) - (22 * 2) / (9 * 2) = 87/18 - 44/18 = 43/18 = 2 7/18;

2) 2 7/8 + 3 1/2 = 43/18 + 7/2 = 43/18 + (7 * 9) / (2 * 9) = 43/18 + 63/18 = 106/18 = 53/9 = 5 8/9.

Ответ: 4 5/6 - 2 4/9 + 3 1/2 = 5 8/9.

№2

3 11/15 - 2 3/5 + 1 9/10 = 3 1/30.

1) 3 11/15 - 2 3/5 = 56/15 - 13/5 = 56/15 - (13 * 3) / (5 * 3) = 56/15 - 39/15 = 17/15 = 1 2/15;

2) 1 2/15 + 1 9/10 = 17/15 + 19/10 = (17 * 2) / (15 * 2) + (19 * 3) / (10 * 3) = 34/30 + 57/30 = 91/30 = 3 1/30.

Ответ: 3 11/15 - 2 3/5 + 1 9/10 = 3 1/30.

№3

(2 3/5 + 1 7/10 + 17/20) * 20 = 123.

1) 2 3/5 + 1 7/10 = 13/5 + 17/10 = (13 * 2) / (5 * 2) + 17/10 = 36/10 + 17/10 = 53/10 = 5 3/10;

2) 5 3/10 + 17/20 = 53/10 + 17/20 = (53 * 2) / (10 * 2) + 17/20 = 106/20 + 17/20 = 123/20 = 6 3/20;

3) 6 3/20 * 20 = 123/20 * 20 = 123.

Ответ: (2 3/5 + 1 7/10 + 17/20) * 20 = 123.

№4

(6 5/12 + 2 2/3 - 5 1/12) * 3/4 = 3.

1) 6 5/12 + 2 2/3 = 77/12 + 8/3 = 77/12 + (8 * 4) / (3 * 4) = 77/12 + 32/12 = 109/12 = 9 1/12;

2) 9 1/12 - 5 1/12 = 109/12 - 61/12 = 48/12 = 4;

3) 4 * 3/4 = 3.

Ответ: (6 5/12 + 2 2/3 - 5 1/12) * 3/4 = 3.