0,5+(3/4-5/6)=5/10+3/4-5/6=30/60+45/60-50/60=25/60=5/12
4 2/9-(5+3 5/6)=4 2/9-5-3 5/6=4 8/36-4 36/36-3 30/36=4-4-3+(8-36-30)/36=
=-3+(-58/36)=-3 58/36=-4 22/36=-4 11/18
17,4-(4 3/5-21,7)=17,4-4 3/5+21,7=17,4-4 6/10+21,7=17,4-4,6+21,7=34,5
10-(2,1+4 3/4)=10-2,1-4 3/4=10-2,1-4 75/100=10-2,1-4,75=3,15