Б)(7/9-1/6):2/9×21/22= в)7/8+5/8×1/3+2/3= г)(1/6+3/14):(5/21-1/14)=

Чтобы выполнить действия, сначала выполним действия в скобках, а потом умножение и деление, а потом прибавление и отнимание:

1. (7/9 - 1/6) : 2/9 * 21/22 = 2 5/8;

1) 7/9 - 1/6 = (7 * 2)/18 - (1 * 3)/18 = 14/18 - 3/18 = 11/18;

2) 11/18 : 2/9 = 11/18 * 9/2 = (11 * 9)/(9 * 2 * 2) = 11/4;

3) 11/4 * 21/22 = (11 * 21)/(4 * 22) = (11 * 21)/(4 * 2 * 11) = 21/8 = 2 5/8.

2. 7/8 + 5/8 * 1/3 + 2/3 = 1 11/12;

1) 5/8 * 1/3 = 5/24;

2) 7/8 + 5/24 + 2/3 = (7 * 3)/24 + 5/24 + (2 * 8)/24 = 21/24 + 5/24 + 16/24 = 42/24 = 21/12 = 1 11/12.

3. (1/6 + 3/14) : (5/21 - 1/14) = 2 6/21;

1) 1/6 + 3/14 = (1 * 7)/42 + (3 * 3)/42 = 7/42 + 9/42 = 16/42 = 8/21;

2) 5/21 - 1/14 = (5 * 2)/42 - (1 * 3)/42 = 10/42 - 3/42 = 7/42 = 1/6;

3) 8/21 : 1/6 = 8/21 * 6 = (6 * 8)/21 = 48/21 = 2 6/21.