Respuesta :

gmany

[tex]3(x-7)-x=2x-21\ \ \ \ |\text{use distributive property}\\\\(3)(x)+(3)(-7)-x=2x-21\\\\3x-21-x=2x-21\ \ \ \ |+21\\\\3x-x=2x\\\\2x=2x[/tex]


Answer: all real numbers. The equation is identity.