3. Вычислите: 1) 5/4 + (-7/4 + 3/4 * 2/7) : 2/9; 2) 2 1/3 + 4/9 * 3 3/8 - 1 6/7 : 26/63; 3) 2 4/15 - (2 - 1 1/15) : 4/9 + 2/3; 4) -1 + (7/12 + 5/6) : 2 5/6 - 2/3;

1. 5/4 + (-7/4 + 6/28) : 2/9 = 5/4 + (-7/4 + 3/14) : 2/9 = 5/4 + (-49/28 + 6/28) : 2/9 = 5/4 + (-43/28) : 2/9 = 5/4 - (43/28) * (9/2) = 5/4 - 387/56 = 70/56 - 387/56 = -317/56.
2. 7/3 + 4/9 * 27/8 - 13/7 : 26/63 = 7/3 + (4*27)/(9*8) - 13/7 * 63/26 = 7/3 + 108/72 - (13*63)/(7*26) = 7/3 + 3/2 - 819/182 = 7/3 + 3/2 - 39/13 = 7/3 + 3/2 - 3 = (14 + 9 - 18)/6 = 5/6.
3. 34/15 - (2 - 16/15) : 4/9 + 2/3 = 34/15 - (30/15 - 16/15) : 4/9 + 2/3 = 34/15 - 14/15 : 4/9 + 2/3 = 34/15 - 14/15 * 9/4 + 2/3 = 34/15 - 126/60 + 2/3 = 34/15 - 21/10 + 2/3 = (68 - 63 + 20)/30 = 25/30 = 5/6.
4. -1 + (7/12 + 10/12) : 17/6 - 2/3 = -1 + 17/12 : 17/6 - 2/3 = -1 + 17/12 * 6/17 - 2/3 = -1 + 6/12 - 2/3 = -1 + 1/2 - 2/3 = (-6 + 3 - 4)/6 = -7/6.