PRE-ALGEBRA
Lesson 74 of 171

VARIABLES AND EXPRESSIONS
Evaluating Expressions
Students learn to evaluate an expression by substituting a value in for the variable or variables. For example, if x = 7, and the given expression is 1 + 9x, substitute a 7 in for x in the given expression, to get 1 + 9(7), or 1 + 63, which equals 64.
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