1) 25/36 + (2/3 - 7/36) = (25/36 - 7/36)+ 2/3 = 18/36 + 2/3 = 1/2 + 2/3 = 3/6 + 4/6 = = 7/6 = 1 целая 1/6;
2) (19/20 + 7/18) + 1/9 = 19/20 + (7/18 + 1/9) = 19/20 + (7/18 + 2/18) = 19/20 + + 9/18 = 19/20 + 1/2 = 19/20 + 10/20 = 29/20 = 1 целая 9/20;
3) (79 + 120 + 7/8) + (13/120 - 23/40) - тут, видимо, ошибка;
(79/120 + 7/8) + (13/120 - 23/40) = (79/120 + 13/120) + (7/8 - 23/40) = = 92/120 + (35/40 - 23/40) = 23/30 + 12/40 = 23/30 + 3/10 = 23/30 + 9/30 =
= 32/30 = 16/15 = 1 целая 1/15
4) (73/80 + 8/9) + (5/18 - 13/80) = (73/80 - 13/80) + (8/9 + 5/18) = 60/80 +
+ (16/18 + 5/18) = 3/4 + 21/18 = 3/4 + 7/6 = 9/12 + 14/12 = 23/12 =
= 1 целая 11/12