Play the instructional video. Then post the following questions and play the video again so that students can look for the answers to the posted questions.
• What is the difference between a mathematical expression and an algebraic expression? (Algebraic expressions are mathematical expressions that include one or more variables, or letters/symbols that stand for numbers.)
• How do you evaluate an expression? (Replace the variable with the given number, then simplify the resulting numerical expression.)
• In the mountain-climbing example, why is multiplication the operation used? (The anchors are spaced at equal intervals of 20 feet.)