Final answer:
An algebraic expression is a collection of numbers and letters that are combined using the four arithmetic operations as well as algebraic operators such as exponents, roots, absolute values, and fraction bars. Variables in an algebraic expression represent unknown values that can vary within a given range.
Step-by-step explanation:
An algebraic expression is a collection of numbers and letters that are combined using the four arithmetic operations as well as algebraic operators such as exponents, roots, absolute values, and fraction bars. It is a way to represent a mathematical relationship or formula. The variables in an algebraic expression represent unknown quantities or values that can vary within a given range. For example, in the expression 3x + 2y, x and y are the variables.