1. **State the problem:** Mandy has a gift card worth 75 and each audiobook costs 3.75. We need to find the remaining balance after purchasing 7 audiobooks and after purchasing 15 audiobooks. 2. **Formula used:** Remaining balance = Initial balance - (Number of audiobooks purchased \times Cost per audiobook) 3. **Calculate remaining balance after 7 audiobooks:** $$\text{Remaining} = 75 - (7 \times 3.75)$$ $$= 75 - 26.25$$ $$= 48.75$$ 4. **Calculate remaining balance after 15 audiobooks:** $$\text{Remaining} = 75 - (15 \times 3.75)$$ $$= 75 - 56.25$$ $$= 18.75$$ 5. **Summary:** - After buying 7 audiobooks, Mandy has 48.75 left on her gift card. - After buying 15 audiobooks, Mandy has 18.75 left on her gift card. This shows how subtracting the total cost of audiobooks from the initial gift card balance gives the remaining balance.