1)6/7-5/9+1/7-2/9
=1-7/9
=2/9
2)17/18-(1/3+5/18+1/4)
=17/18-(6/18+5/18+1/4)
=6/18-1/4
=1/3-1/4
=1/12
3)1-(7/50+3/20)+16/26
=1-(14/100+15/100)+8/13
=1-29/100+8/13
=71/100+8/13
=(71*13+800)/1300
=1723/1300
1)6/7-5/9+1/7-2/9
=1-7/9
=2/9
2)17/18-(1/3+5/18+1/4)
=17/18-(6/18+5/18+1/4)
=6/18-1/4
=1/3-1/4
=1/12
3)1-(7/50+3/20)+16/26
=1-(14/100+15/100)+8/13
=1-29/100+8/13
=71/100+8/13
=(71*13+800)/1300
=1723/1300