11 7/12 - 5 20/21=? 21 7/18 - 1 1/24=? 13

Вычислим разность смешанных чисел:

1) 11 7/12 - 5 20/21 = 11 5 + 7/12 20/21 = 6 + 7/12 20/21 = 6 + 7 * 7/84 21 * 4/84 = 6 + 49/84 48/84 = 6 + 1/84 = 6 1/84;

2) 21 7/18 - 1 1/24 = 21 1 + 7/18 1/24 = 20 + 7 * 4/72 1 * 4/72 = 20 + 28/72 4/72 = 20 + 24/72 = 20 + 12/36 = 20 2/6 = 20 1/3;

3) 13 1/3 - 9 13/24 =  13 9 + 1/3 13/24 = 4 + 1/3 13/24 = 4 + 1 * 8/24 13/24 = 4 + 8/24 13/24 = 4 5/24 = 3 + 24/24 5/24 = 3 19/24.