2.169. Вычислите: а) 23/24 − (1/6 + 1/4); б) 4/35 + (3/5 − 4/7); в) 11/15 − (2/3 − 3/20); г) 5/18 + (2/9 + 1/27).

а) 1/6 + 1/4 = 5/12; 23/24 − 5/12 = 23/24 − 10/24 = 13/24.

б) 3/5 − 4/7 = 21/35 − 20/35 = 1/35; 4/35 + 1/35 = 1/7.

в) 2/3 − 3/20 = 40/60 − 9/60 = 31/60; 11/15 − 31/60 = 44/60 − 31/60 = 13/60.

г) 2/9 + 1/27 = 7/27; 5/18 + 7/27 = 15/54 + 14/54 = 29/54.