5.b)3/4-(1/2)•2=1/4
3/4-2/4=1/4
6.a) (x-y)-z=(12,5-25/3)-1/4
=[(125/10)/5-(25/3)2]-1/4
=[(25/2)3-50/6]-1/4
=(75/6-50/6) -1/4
=(25/6)2-(1/4)3
=50/12-3/12=47/12
x-(y-z)=12,5-(25/3-1/4)=
=(125/10)/5-[(25/3)4-(1/4)3]=
=25/2-(100/12-3/12)= (25/2)6-97/12=
=150/12-97/12= 53/12
(x-y)-z<x-(y-z)
47/12<53/12
