In the question, the given expression is
[tex]z+(z+6)[/tex]
And we have to find the equivalent expression to the given expression .
First we remove the parenthesis
[tex]z+z+6[/tex]
Now we combine the like terms, and here like terms are z and z, therefore on combining , we will get
[tex]z+z+6 = 2z+6[/tex]
And that's the required equivalent expression .