а) (8 7/12 - 2 17/36) 2.7 - 4 1/3 : 0.65
Переведем все числа в дроби: 8 7/12 = 99/12, 2 17/36 = 89/36, 4 1/3 = 13/3.
Тогда выражение будет равно: ((99/12 - 89/36) 2.7 - 13/3) / 0.65 =
= ((297/36 - 89/36) 2.7 - 13/3) / 0.65 =
= (208/36 2.7 - 13/3) / 0.65 =
= (18720/36 - 13/3) / 0.65 =
= (520 - 13) / 0.65 =
= 507 / 0.65 =
= 780.

б) (1 11/24 + 13/36) 1.44 - 8/15 0.5625
Переведем все числа в дроби: 1 11/24 = 35/24, 8/15 = 16/30 = 16/30, 0.5625 = 9/16.
Тогда выражение будет равно: ((35/24 + 13/36) 1.44 - 16/30 9/16) =
= (1058/900 * 1.44 - 144/240) =
= (1272/900 - 144/240) =
= (636/450 - 36/60) =
= (1272/900 - 144/240) =
= (318/225 - 36/60) =
= (318/225 - 36/60) =
= (318/225 - 36/60) =
= (318/225 - 36/60) =
= (318/225 - 36/60) =
= 1.52.