a) 11/4 + 5/6 + 2/5= (numitor comun 60)
=165/60 + 50/60 + 24/60=
=239/60
b) 7/30 + 5/6 + 4/15 + 1/2= (numitor comun 30)
=7/30 + 25/30 + 8/30 + 15/30 =
=55/30 = 11/6
c) 1/4 + 1/2 + 3/8 + 5/12= (numitor comun 24)
= 6/24 + 12/24 + 9/24 + 10/24 =
= 37/24