Обчислити 4 2/3- 6 3/7-(-1 2/9)+5 10/21

= 4 6/9+ 1 2/9 - 6 9/21 + 5 10/21 = 5 8/9 - 20/21 = 5 56/63 - 60/63 = 4 119/63 - 60/63 = 4 59/63