Выполните сложение 7/20+8 3/4, 8 3/5+1 9/10, 6 2/3+8 5/7

Выполним сложение и вычислим его значение:

1) 7/20 + 8 3/4 = 7/20 + 8 + 3/4 = 8 + (7 * 1 + 3 * 5)/20 = 8 + (7 + 15)/20 = 8 + 22/20 = 8 + 20/20 + 2/20 = 8 + 1 + 1/10 = 9 + 1/10 = 9 1/10; 

2) 8 3/5 + 1 9/10 = 8 + 1 + 3/5 + 9/10 = 9 + 3/5 + 9/10 = 9 + (3 * 2 + 9 * 1)/10 = 9 + (6 + 9)/10 = 9 + 15/10 = 9 + 10/10  + 5/10 = 9 + 1 + 1/2 = 10 + 1/2 = 10 1/2; 

3) 6 2/3 + 8 5/7 = 6 + 8 + 2/3 + 5/7 = 14 + 2/3 + 5/7 = 14 + (2 * 7 + 5 * 3)/21 = 14 + (14 + 15)/21 = 14 + 29/21 = 14 + 21/21 + 8/21 = 14 + 1 + 8/21 = 15 + 8/21 = 15 8/21.