1) 7/18 x 9/14 = 1/4
1/3 x 6/7 = 2/7
1/4 + 2/7 (приводим к общ. знаменателю - 28) = 7/28 + 8/28 = 15/28
2)3 3/4= 15/4
15/4 x 2/5 = 3/2
3 6/25 x 5/27 = 81/25 x 5/27 = 3/5
3/2 - 3/5 = 9/10 = 0.9
3)1 17/28 x 14/9 = 45/28 x 14/9 = 5/2
14/25 x 5/7 = 2/5
5/2 + 2/5 = 29/10 = 2.9