Final answer:
To find out how many more pencils Daphne will need to fill at least 15 boxes, we can use the inequality: 5x ≥ 40.
Step-by-step explanation:
To find out how many more pencils Daphne will need to fill at least 15 boxes, we can use an inequality. Let x represent the number of additional boxes she needs to fill.
Since each box holds 5 pencils, the total number of pencils she needs will be 5 multiplied by the total number of boxes she needs to fill.
So, the inequality will be: 5x ≥ (15 - 7)×5. Simplifying, we get: 5x ≥ 8×5.
And further simplifying, we get: 5x ≥ 40. This inequality indicates that Daphne will need at least 40 more pencils to fill at least 15 boxes.