з) (20 - 19 3/4) + (17 3/4 - 17) + (2 1/2 - 17/24)

(19 4/4 - 19 3/4) + 3/4 + (2 12/24 - 17/24) = 1/4 + 3/4 + (1 36/24 - 17/24) = 1 + 1 19/24 = 2 19/24