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Se stie ca: x+y=23 si z=15 calculati xz+yz
Se stie ca :x-y=12 si z=10 calculati xz-yz
se stie ca: ab+ac=420 si b+c=14 aflati a
se stie ca : ab-ac-135 si a-9 aflati b-c


Răspuns :

xz+yz= z(x+y)= 15 · 23= 345
xz-yz=z(x-y)=10·12=120
ab+ac=a(b+c)=420 => a·14=420 => a=420:14 a= 30
ab-ac=a(b-c)=135 => 9(b-c)=135 => b-c= 135:9 b-c= 15