1. **State the problem:** Jeremy has an $8 gift card and wants to buy comic books costing $5.25 each. The function $f(x) = 5.25x - 8$ gives the cash needed to buy $x$ comic books. 2. **Identify what is asked:** Find the cash needed to buy 3 comic books, i.e., calculate $f(3)$. 3. **Apply the function:** Substitute $x=3$ into the function: $$f(3) = 5.25 \times 3 - 8$$ 4. **Calculate multiplication:** $$5.25 \times 3 = 15.75$$ 5. **Calculate subtraction:** $$15.75 - 8 = 7.75$$ 6. **Interpretation:** Jeremy needs $7.75$ in cash after using his $8 gift card to buy 3 comic books. **Final answer:** $7.75$