The expression "3x + 5" is a simple algebraic equation where "x" represents a variable. The number "3" is a coefficient, meaning it multiplies the variable "x." The "+ 5" indicates that 5 is added to the product of 3 and x. This expression can represent various values depending on what "x" is. In mathematics, expressions like "3x + 5" are often used in equations to solve for unknowns. For example, if you set "3x + 5" equal to another number, you can find the value of "x." This process is fundamental in algebra, a branch of mathematics that deals with symbols and the rules for manipulating those symbols.