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daca a+ b= 19, b+ c= 21, a+ c= 20. Calculati a+ b + c

Răspuns :

a+ b= 19
b+ c= 21
a+ c= 20
a+b+b+c+a+c=19+21+20
2(a+b+c)=60
 a+ b + c =30
c=30-19=11
a=30-21=9
b=30-20=10