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(x+12)•13-(x+12)•9=80

Răspuns :

(13x+156)-(9x+108)=80
4x+48=80
4x=80-48
4x=32
x=32:4
x=8

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