Question 74346
An expression is made up of one,two,or more terms,such as 
    2x  3x+2   5x-2y+4
What makes these expressions and not equations is that there is no equal sign.
These are equations:  2x=10  3x+2=8  5x-2y+4=0
Equations can be solved, expressions can not be. They can only be simplified if they contain like terms, such as 2x+5x. The simplification is 7x,but it is still an expression.