1/3 din 3/7 = 1/3 x 3/7 = 1/7
3/4 din 4/3 = 3/4 x 4/3 = 1
5/7 din 15/19 = 5/7 x 15/19 = 75/133
2 si 2/3 din 11/45 = (2+2/3) x 11/45 = 8/3 x 11/45 = 88/135
1 si 4/5 din 2 si 1/27 = (1si4/5) x (2si1/27) = 9/5 x 55/27 = 1/1 x 11/3 = 11/3 = (9+2)/3 = 9/3 + 2/3 =3 si 2/3