1) 3/7*(1/4+4/9)=25/84
1/4+4/9=9/36+16/36=25/36
2) 3/7*25/36=1/7*25/12=25/84
2) 4/5-1/4/ 5/6=1/2
1) 1/4/5/6=1/4*6/5=6/20=3/10
2) 4/5-3/10=8/10-3/10=5/10=1/2
1) 3/7*(1/4+4/9)=25/84
1/4+4/9=9/36+16/36=25/36
2) 3/7*25/36=1/7*25/12=25/84
2) 4/5-1/4/ 5/6=1/2
1) 1/4/5/6=1/4*6/5=6/20=3/10
2) 4/5-3/10=8/10-3/10=5/10=1/2