Question

un pix si o carte costa 10 lei,cartea si un caiet costa 9 lei,iar caietul si pixul costa 5 lei.Determianti pretul cartii

Answer 1

Notam:  cartea=a      pix=b  si  caietul=c

a+b=10       a=10-b             a=10-b             a=10-3            a=7

a+c=9        10-b+c=9          b=c+1               b=2+1             b=3 

b+c=5         b+c=5               c+1+c=5          2c=4                c=2