fieb=grinda brad is s=grinda stejar atunci 7b+12s=750 si 14b+24s=1500 mai avem 3b+8s=450 si 9b+24s=1350 atunci scazand din prima a doua obtinem 14b-9b=1500-1350 adica 5b=150 si b=30kg. 8s=450-3×30=360 adica s=360:8=45kg deci bradul=30kg si stejarul=45kg