Ответ:

Пошаговое объяснение:

1/3+1/4+1/5 => НОК(3;4;5)=60=>  (20+15+12)/60 = 47/60.

1/5+1/6+1/7 => НОК(5;6;7) = 210 => (42+35+30)/210 = 107/210.

2/3+3/5+1/2 = > НОК(3;5;2) = 30 => (20+18+15)/30 =53/30 = 1 23/30.

5/7+4/7+4/5 => НОК(7;7;5) = 35 => (25+20+28)/35 = 73/35 = 2 3/35.