5 11/14 х - 8/15=5/21 3 х=2/9 18/49: х=6/35

1) 5 11/14 * х - 8/15 = 5/21;

(5 * 14 + 11) / 14 * х = 5/21 + 8/15;

81/14 * х = 5 * 5/105 + 7 * 8/105;

х = (25 + 56) / 105 : 81/14 = 81/105 * 14/81 = (81 * 14) / (105 * 81) = 14/105 = 2/15;

Ответ: х = 2/15.

2) 3 * х = 2/9;

х = 2/9 : 3 = 2/27;

Ответ: х = 2/27.

3) 18/49 : х = 6/35;

х = 18/49 : 6/35 = 18/49 * 35/6 = (18 * 35) / (49 * 6) = (3 * 5) / 7 = 15/7;

Ответ: х = 15/7.