3/10 · 28/9 :14/30=
= 1/5 · 14/3 · 30/14 = (am simplificat in cruce cu 2 si cu 3- la inmultire, impartirea inseamna inmultirea cu inversul)
=14/15 ·30/14=
=1/1 ·2/1=2
6/112 + 3/56 : 1/4=
= 3/56 + 3/56 · 4/1=
= 3/56 + 12/56=
=15/56
4/15+ 7/20 - 1/6= (numitor comun 60)
= 16/60 + 21/60 - 10/60=
= 27/60= 9/20
1/5 + 2/5 :1/5 -1/5=
= 1/5 +2/5 · 5/1 -1/5=
= 10/5= 2
1/4 : 1/4 · 1/4 + 1/4=
= 1 · 1/4 + 1/4=
=1/4 + 1/4=
= 2/4 = 1/2