To have an equation, you need to have two expression, and an equal sign (=) between them.
This is not an equation, but rather an expression. In order to simplify it, you simply have to subtract [tex] b [/tex] from the quantity in the parenthesis:
[tex] (2b+1)-b = 2b+1-b = 2b-b+1 = b+1 [/tex]
