An expression is not solved but simplified!

To simplify means that you don't get a numerical result but again letters and numbers and plus or minus signs!

But you do evaluate an expression when you substitute the given values for the variables and then follow the order of operation: always perform the operations in the parentheses first!

To simplify and expression, add or subtract like terms only: same letters (' groups) with exactly same exponent(s). The coefficients (the numbers before the term) can change.

An expression is simplified when all unnecessary parentheses have been removed and like terms are combined!