A) a/3=b/7=k⇒a=3k,b=7k si inlocuind in :
3a-b=6⇔9k-7k=6⇔2k=6⇔k=3
a=9,b=21
B)42kg.....................................39 l suc
x kg.......................................14 l suc
------------------------------------------------Marimile fiind direct proportionale:
42/39=x/14⇒x=42·14/39=196/13 =15+1/13 kg≈15,07 kg