(1 1/2 + 2/3)х6 = (3/2 + 2/3)х6 = (9/6 + 4/6)х6 = 13/6х6=13 ;
(2 1/2 + 1 1/3) : 1/6 - 2 3/7 =( 5/2 +4/3) :1/6 - 2 3/7 = (15/6 + 8/6) :1/6 - 2 3/7 =
= 23/6 :1/6 - 2 3/7 = 23 - 2 3/7 = 20 4/7
(1 3/5 + 2 1/5): 1 9/10 + (1 7/10 - 4/5): 3/7 = 3 4/5 :1 9/10 + (17/10 - 8/10) : 3/7 =
= 19/5 Х 10/19 + 9/10 Х 7/3 = 2 + 2 1/10 = 4 1/10 ;
1 8/9:(3 1/6-1 3/4)= 1 8/9:(19/6 - 7/4) = 1 8/9: 38-21/12 = 1 8/9:17/12 =
= 17/9 Х 12/17 = 12/9 = 4/3 = 1 1/3