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

2 5/9-1 20/21=2-1 +5/9-20/21=1+35/63-60/63=1+(-25/63)=63/63-25/63=38/63
1 8/9:6=17/9*1/6=17/54
38/63:1 8/49=38/63*49/57=2/9*7/3=14/27
14/27+17/54=28/54+17/54=45/54=5/6