Решите 2 уравнения: (2\3x-2\5)*15=8.2\3х+7\3х=18.Найдите значение выражения:21\25*5\7-3\16*4\155 целых5\12*4\13-2 целых5\8*3\14

1) (2/3х - 2/5) * 15 = 8;

2/3х * 15 - 2/5 * 15 = 8;

2 * 5х - 2 * 3 = 8;

10х - 6 = 8;

10х = 8 + 6;

10х = 14;

х = 14 : 10;

х = 1,4.

2) 2/3х + 7/3х = 18;

(2 + 7)/3х = 18;

9/3х = 18;

3х = 18;

х = 18 : 3;

х = 6.

3) 21/25 * 5/7 - 3/16 * 4/15 = (7 * 3 * 5)/(5 * 5 * 7) - (3 * 4)/(4 * 4 * 3 * 5) = 3/5 - 1/20 = 12/20 - 1/20 = 11/20;

4) 5 5/12 * 4/13 - 2 5/8 * 3/14 = (5 * 12 + 5)/12 * 4/13 - (2 * 8 + 5)/8 * 3/14 = (60 + 5)/12 * 4/13 - (16 + 5)/8 * 3/14 = 65/12 * 4/13 - 21/8 * 3/14 = (13 * 5 * 4)/(4 * 3 * 13) - (7 * 3 * 3)/(8 * 2 * 7) = 5/3 - 9/16 = 80/48 - 27/48 = 53/48 = 1 5/48.