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(x+12)•13-(x+12)•9=80

Răspuns :

13x+156 - 9x- 108=80
4x+48=80
4x=32
x= 8
[tex](x+12)*13-(x+12)*9=80 \\ 13x+156-9x+108=80 \\ 4x+48=80 \\ 4x=32 \\ x= \frac{32}{4}= 8 \\ BlackBook[/tex]