Writing and Evaluating Expressions

An expression is a mathematical phrase — a recipe written in symbols. In 0.5n − 3n + 25, n is the variable, 0.5 and −3 are coefficients, and 25 is the constant. Students learn to translate words into expressions, substitute values to evaluate them, and simplify by collecting like terms. This is the bridge between the arithmetic of earlier grades and the equation solving that follows.