Пошаговое объяснение:

№1

1) 23/80 + 45/60 = 23/80 + 3/4 = 23/80 + 60/80 = 83/80 = 1 3/80

2) 20/45 + 26/54 = 4/9 + 13/27 = 12/27 + 13/27 = 25/27

3) 36/300 + 12/40 - 350/1000 = 3/25 + 3/10 - 7/20 = 12/100 + 30/100 - 35/100 = 7/100

№2

1) 1/2 - 1/4 = 2/4 - 1/4 = 1/4

2) 1/4 : 1/8 = 1/4 * 8/1 = 8/4 = 2

№3

1) 1 5/9 : 7/24 = 14/9 * 24/7 = 2/3 * 8/1 = 16/3 = 5 1/3

2) 7 - 5 1/3 = 6 3/3 - 5 1/3 = 1 2/3

3) 1 2/3 * 1 7/20 = 5/3 * 27/20 = 1/1 * 9/4 = 9/4 = 2 1/4