Răspuns :
a+b=600
a-b=120
⇒a=b+120;
⇒[b+120]+b=600
⇒b+b=600-120
⇒2b=480
⇒b=480/2
⇒b=240;
⇒a=b+120
⇒a=240+120
⇒a=360;
sau a=600-b
⇒a=600-240
⇒a=360;
Verificare 360+240=600; 360-240=120;
a-b=120
⇒a=b+120;
⇒[b+120]+b=600
⇒b+b=600-120
⇒2b=480
⇒b=480/2
⇒b=240;
⇒a=b+120
⇒a=240+120
⇒a=360;
sau a=600-b
⇒a=600-240
⇒a=360;
Verificare 360+240=600; 360-240=120;