Răspuns:
prima metoda:
9+{13-[5+(7-2)]}= 9+ [13-(5+5)]=9+(13-10)=9+3=12
a doua metoda:
9+{13-[5+(7-2)]}= 9+ [13-(5+5)]=9+(13-10)= (9+13)-(9+10)= 22-19=12