## IM Commentary

The purpose of this series of two tasks (the previous one is here) is to highlight that while a numerical expression can only take one value, an algebraic expression can take many different values depending on the value of the variable. Furthermore, once you place that expression in a equation, it's possible that there can only be one value for the variable that makes the equation true. (It's also possible that the equation can be always true, as in $2x \div 3 = \frac23 \cdot x$, or never true, as in $x=x+8$, but this task doesn't get into that idea.) All work is done out of a context with positive whole numbers, so that discussion can focus on the shift from numerical to algebraic expressions.

In parts (a) and (b), students new to working with exponents may need some help evaluating the expressions correctly. They should know to "do the parentheses first" from previous grades, but may need reminding that by convention we evaluate exponents before we add.

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