5.
A={6,7,8,9,10,11,12...}
B={11,12,13,14...}
A∩B={11,12,13,...}
6.
a)36/72 = x/y
36/72 se simplifica cu 36 si devine 1/2 =>
x/y=1/2
b)xy=12 (produsul mezilor=produsul extremilor)
=>4·12-20=48-20=28
c)(10a+3+10b+4+10c+5)/(10a+3+10b+7+10c+2)=
(10a+10b+10c+12)/(10a+10b+10c+12)=1 da, este echiunitara.
