1) 2 5/9-1 20/21=2 35/63-1 60/63=38/63
38/63:1 8/49=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
2) 1 17/18*1 13/14=35/18*27/14=15/4=3 3/4
2 5/8:1 19/20=21/8*20/39=105/78=1 27/78
3 3/4-1 27/78=3 117/156-1 54/156=2 63/156
2 25/78-1 1/26=2 25/78-1 3/78=1 22/78=1 11/39
2 63/156:1 11/39=375/156*39/50=15/8=1 7/8
3) 4 2/9x=6 11/21-3 5/14
4 2/9x=6 22/42-3 15/42
4 2/9x=3 7/42=3 1/6
x=3 1/6:4 2/9=19/6*9/38
x=3/4