21)
a) 2/3 + 4/3 = (2+4)/3 = 6/3
b) 13/9 + 4/9 + 1/9 = (13+4+1)/9 = 18/9 = 2
c) 17/8 - 5/8 = (17 -5)/8 = 12/8 = 3/2
d) 41/7 - 5/7 -8/7 = (41-5-8)/7 = 28/7 = 4
e) 3/4 × 8/9 = 2/3 (se simplifica 8 cu 4 si 9 cu 3)
f) 15/11 × 2/3 × 22/5 = 2×22/11 = 44/11 = 4
(am simplificat 15 cu 5 si 3 cu 3)
g) 15/22 : 20/11 =
= 15/22 × 11/20 =
= 15/2×20 = 15/40 = 3/8
h) 35/33 : 5/11 :7/3 =
= 35/33 × 11/5 ×3/7 =
= 35/5×7 =
= 35/35 =
= 1
