Let's begin by listing out the information given to us:
Kimberly has $120; Total Amount = $120
Kimberly buys a hardcover book for $36
Amount left = Total Amount - hardcover book cost = 120 - 36 = $84
Amount left = $84
Each gift card is $15
To know how many gift cards Kimberly can buy, we divide the Amount left by the cost of each gift card
[tex]\begin{gathered} \frac{84}{15}=5.6 \\ \text{Gift card can only be an integer not decimal} \\ As\text{ such, we have to round down}\Rightarrow5.6\text{ }\cong5 \\ x\leq5\text{ } \end{gathered}[/tex]