hello
to solve this question, we'll approach it just like a regular equation
[tex]\begin{gathered} \mleft|2b-4\mright|=2b-4 \\ \text{collect like terms} \\ 2b-2b=-4+4 \\ 0=0 \\ \text{one of the pair has a symbol}\mleft|\square\mright|.\text{ this is known as the absolute value} \\ \text{and it implies the value in there would be resolved and it'll be positive} \end{gathered}[/tex]