a) 1/5 -1/8 (aducem la acelasi numitor) = 8/40 - 5/40 = 3/40
b) 1/3 - 1/4 (la fel aducem... ) = 4/12 - 3/12 = 1/12
c) 11/2 - 2/3 - 1/5 = 165/30 - 20/30 - 6/30 = 139/30
d) 1/2 - 1/8 = 8/16 - 2/16 = 6/16
e) 2/3 - 1/6 = 4/6 - 1/6 = 3/6 = 1/2
f) 11/4 - 1/6 - 5/12 = 33/12 - 2/12 - 5/12 =26/12 =13/6
g) 4/15 - 1 /10 = 8/30 - 3/30 = 5/30 = 1/6
h) 21/8 - 11/12 - 1/6 = 63/24 - 22/24 - 4/24 = 37/24
i) 31/5 - 11/10 - 4/15 = 186/30 - 33/30 - 8/30 = 145/30 = 29/6