Răspuns :
a+b=12920
a-b=12900
din a+b=12920 =>a=12920-b si inlocuim in a doua ecuatie
12920-b -b=12900
-2b=12900-12920
-2b= -20
b=-20 : (-2)
b=10
a+b=12920
a-b=12900
din a+b=12920 =>a=12920-b si inlocuim in a doua ecuatie
12920-b -b=12900
-2b=12900-12920
-2b= -20
b=-20 : (-2)
b=10