When we are simplifying like terms we see all the terms that have the same literal parts meanig we add all the letters together.
Example
[tex]5x+6x=11x[/tex]when we have different letters in the expression they cannont be added,
[tex]5w+3w+2w+7v[/tex]in this expression the like terms will be all the ones that have a w, so we add them together and leave the 7v as it is
[tex]\begin{gathered} (5w+3w+2w)+7v \\ 10w+7v \end{gathered}[/tex]