3. a) 3/10, 5/12, 5/6 - 60 este numitor comun
18/60, 25/60, 50/60
b) 1/2, 2/3, 3/5, 7/30 - 30 este numitor comun
15/30, 20/30, 18/30, 7/30
c) 1/2, 3/4, 5/18 - 36 este numitor comun
18/36, 27/36, 10/36
4. 3/4 < 2/3 < 7/10 < 5/6 < 11/12
5. a) 2/3 + 3/4 + 7/10 = 40/60 + 45/60 + 42/60 = 127/60 = 2 si 7/60
b) 7/8 - (1/2 - 1/4) = 7/8 - (2/4 - 1/4) = 7/8 - 1/4 = 7/8 - 2/8 = 5/8
c) (3 si 3/8 + 1 si 1/6) - (2 si 2/3 + 1/4) = (27/8 + 7/6) - (8/3 + 1/4) =
(81/24 + 28/24) - (32/12 + 3/12) = 109/24 - 35/12 = 109/24 - 70/24 =
39/24
6. 2/7 + 2/5 + 3/7 + 1/5 + 2/7 + 7/5 =
(2/7 + 3/7 + 2/7) + (2/5 + 1/5 + 7/5) =
7/7 + 10/5 =
1 + 2 =
3
