The target model multiplies a unit rate by a quantity and then subtracts a fixed amount. Evaluate Situations A–E, then report the \(\text{complete}~\text{matching}~\text{set}\).
A. Bike rental costs \(\$6~\text{per}~\text{hour}\) with \(\$8~\text{off}~\text{the}~\text{total}\).
B. Concert tickets cost \(\$24~\text{each}\) and \(3\) are bought.
C. Earnings are \(\$15~\text{per}~\text{lawn}\), followed by \(\$12~\text{spent}~\text{on}~\text{gas}\).
D. \(\text{Each}~\text{bottle}\) holds \(750~\text{milliliters}\) and \(3~\text{bottles}\) are poured.
E. A plan costs \(\$9~\text{per}~\text{month}\) plus a \(\$20~\text{sign}\text{-}\text{up}~\text{fee}\).
What this problem is really about
Translate the target into an expression skeleton: a per-unit rate times a varying quantity, followed by subtracting one constant amount. Test each situation for all three roles, paying special attention to the sign of any fixed fee. Multiplication alone is incomplete, and a fixed amount added afterward has a different structure even when the story sounds similar.