a) 1 5/6 - 2(9/8 - 2 5/6) = 1 20/24 - 2(27/24 - 2 20/24) = 1 20/24 - 2(27/24 - 68/24) = 1 20/24 - 2*(-41/24) = 1 10/12 + 41/12 = 1 10/12 + 3 5/12 = 4 15/12 = 5 3/12 = 5 1/4
b) (2 2/9 - 3 1/3) : (-6 2/3) = (2 2/9 - 3 3/9) : (-6 6/9) = (20/9 - 30/9) : (-60/9) = (-10/9) * (-9/60) = 1/6