1-(1/6+1/3)=1-3/6=1/2
2-3/7+4/7=14/7-3/7+4/7=15/7
3/4-1/3-3/8=18/24-8/24-9/24=1/24
68-7.5+32-2.5=60.5+32-2.5=92.5-2.5=90
5/12-(1/12-1/2)=5/12-(1/12-6/12) =5/12-(-5/12)=10/12=5/6
1-(1/6+1/3)=1-3/6=1/2
2-3/7+4/7=14/7-3/7+4/7=15/7
3/4-1/3-3/8=18/24-8/24-9/24=1/24
68-7.5+32-2.5=60.5+32-2.5=92.5-2.5=90
5/12-(1/12-1/2)=5/12-(1/12-6/12) =5/12-(-5/12)=10/12=5/6