Найдите значение выражения (2 5/9-1 20/21): 1 8/49+1 8/9: 6

(2 5/9-1 20/21):1 8/49+1 8/9:6=5/6
2 5/9-1 20/21=2 35/63-1 60/63=1-25/63=63/63-25/63=38/63
38/63:1 8/49=38/63:57/49=38/63*49/57=14/27
1 8/9:6=17/9*1/6=17/54
14/27+17/54=28/54+17/54=45/54=5/6