9/56-(7/15-5/12)*(3/14+1/2), (2/3+7/8-5/6)*(1-5/17), (2 1/2)в2 ступени*8/15-5/9

9/56 - (7/15 - 5/12) * (3/14 + 1/2) = 1/8.

1) 7/15 - 5/12 = (7 * 4)/60 - (5 * 5)/60 = 28/60 - 25/60 = 3/60 = 3/(3 * 20) = 1/20;

2) 3/14 + 1/2 = 3/14 + 7/14 = 10/14 = (2 * 5)/(2 * 7) = 5/7;

3) 1/20 * 5/7 = (1 * 5)/(5 * 4 * 7) = 1/28;

4) 9/56 - 1/28 = 9/56 - 2/56 = 7/56 = 7/(7 * 8) = 1/8.

(2/3 + 7/8 - 5/6) * (1 - 5/17) = 5/17.

1) 2/3 + 7/8 = 16/24 + 14/24 = 30/24;

2) 30/24 - 5/6 = 30/24 - (5 * 4)/24 = 30/24 - 20/24 = 10/24 = 5/12;

3) 1 - 5/17 = 17/17 - 5/17 = 12/17;

4) 5/12 * 12/17 = 5/17.

(2 1/2)^2 * 8/15 - 5/9 = 2 7/9.

1) (2 1/2)^2 = (5/2)^2 = 25/4;

2) 25/4 * 8/15 = (5 * 5 * 4 * 2)/(4 * 5 * 3) = 10/3 = 3 1/3;

3) 3 1/3 - 5/9 = 10/3 - 5/9 = 30/9 - 5/9 = 25/9 = 2 7/9.