An expression is a mathematical “phrase.” Expressions contain numbers and variables, but not an equal sign. An equation has an “equal” sign.
When we simplify an expression, we work until there are as few terms as possible. This process makes the expression easier to use, (that’s why it’s called “simplify”). The first thing we want to do when simplifying an expression is to combine like terms.
An equation has an equal sign. The goal of solving equations is to get the variable by itself, to SOLVE for x =. In order to do this, we must “undo” what was done to the problem initially. Follow reverse order of operations – look for addition/subtraction first, then multiplication/division, then exponents, and parenthesis. The important rule when solving an equation is to always do to one side of the equal sign what we do to the other.