А) (5/8 - 2/5) + 3/20 = 3/8
1. 5/8 - 2/5 = 9/40
2. 9/40 + 3/20 = 15/40 = 3/8
Б) 1/8 + (5/9 - 1/4) = 31/72
1. 5/9 - 1/4 = 11/36
2. 1/8 + 11/36 = 31/72
В) 5/6 - (3/10 + 2/5) = 2/15
1. 3/10 + 2/5 = 7/10
2. 5/6 - 7/10 = 4/30 = 2/15
Г) (3/4 + 1/8) - 5/8 = 2/8
1. 3/4 + 1/8 = 7/8
2. 7/8 - 5/8 = 2/8