Doar ex. 4 de restul n-am timp , scuze.
4)b/3=2/a
ab=6
2/a=3/a+c
2a+2c=3a
2a-3a=-2c
-a=-2c |x (-1)
a=2c
inlocuim in ab=6
2c x b =6
c x b = 6/2
c x b =3
<=>
bc=3
