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afla numarul x,stiind ca :xa+xb=20 si a+b=5

Răspuns :

2x + a+B=20
2x+5=20
2x=20-5
2x=15
X=15:2
X=7,5

7,5(x)+2,5(a)+7,5(x)+2,5(B)= 20