(1\2 - 1\5)-(1\3-3\4)
(1/2 - 1/5) - (1/3 - 3/4) = (5/10 - 2/10) - (4/12-9/12) = 3/10 - (-5/12) = = 3/10 + 5/12 = 18/60 + 25/60 = 43/60