15. Jayden bought 70 feet of speaker wire for \( \$ 18.20 \). He needs 30 more feet. If the unit price is the same, how much will Jayden pay for the extra 30 feet of wire? Explain.

To find the cost of the additional 30 feet of speaker wire, we start by determining the unit price of the wire. Jayden bought 70 feet for \$18.20, so the unit price is calculated as: \[ \text{Unit Price} = \frac{\$18.20}{70 \text{ feet}} = \$0.26 \text{ per foot} \] Now, to find the cost for the extra 30 feet, we multiply the unit price by the number of feet needed: \[ \text{Cost for 30 feet} = 30 \text{ feet} \times \$0.26 \text{ per foot} = \$7.80 \] So, Jayden will pay \$7.80 for the additional 30 feet of speaker wire.