## Algebraic Reasoning

As students have already learned, arithmetic expressions contain numbers, grouping symbols, and operation symbols, while algebraic expressions contain these as well as unknown values represented by variables. To evaluate an expression means to find its value. When an expression contains a variable, a given value must be substituted for the variable before the expression can be evaluated. The expressions in this chapter focus on multiplication and division. The equations in this chapter are simple enough to be solved by inspection, by using related number sentences, or by using a guess-and-check strategy. Remind students that the multiplication symbol is often omitted in expressions and equations. Thus, 2 × a can be written as 2a, and 23 × b as 23b.

**Teaching Model 5.2:** Words Into Expressions Algebra