a-b=40 a/3=2b/5 scrii a in functie de b, astfel daca inmultesti ecuatia cu 3 iti da a=6b/5 inlocuiesti in prima ecuatie 6b/5-b=40 aduci la acelasi numitor b/5=40 b=8 a-8=40 a=48

a-b=40 a·1/3=b·2/5=k ⇒a·1/3=k⇒a=k/1/3⇒a=k·3⇒a=3k; ⇒b·2/5=k⇒b=k/2/5⇒b=k·5/2⇒b=5k/2; ⇒3k-5k/2=40 ⇒6k/2-5k/2=40 ⇒k/2=40 ⇒k=2·40 ⇒k=80; ⇒a=3k⇒a=3·80⇒a=240; ⇒b=5k/2⇒b=5·80/2⇒b=5·40⇒b=200;