[tex]12(3x+4y+5)-12(-3x+4y-5)=\\=36x+48y+60-(-36x)-48y-(-60)=\\=36x+48y+60+36x-48y+60=\\=\boxed{72x+120}[/tex]
12(3x + 4y + 5) -12 (-3x + 4y -5)=
36x + 48y + 60 + 36x - 48y + 60 =
72x + 120
miłego:)
