А)
(5/12 + 1/6 + 3/8) : 15/16 =
= (10/24 + 4/24 + 9/24 : 15/16 = 23/24 : 15/16 =
= (23•16)/(24•15) = (23•2)/(3•15) = 46/45 = 1 1/45 ( 1 целая 1/45)
Б)
1/2 + 3/4 • 8/15 - 3/10 =
= 1/2 + (3•8)/(4•15) -3/10 =
= 1/2 + (1•2)/(1•5) - 3/10 =
= 1/2 + 2/5 - 3/10 =
= 5/10 + 4/10 - 3/10 = 9/10 - 3/10 = 6/10 = 3/5