40% discount means Dave pays 60% of the usual price.<br><br>
&bull; Percentage paid = 100% − 40% = 60%<br>
&bull; Price paid = 60% of $15 = \(\frac{60}{100} \times 15\) = 0.6 × 15 = $9<br>
&bull; Alternatively: Discount = 40% of $15 = $6; Price paid = $15 − $6 = $9<br><br>
Final Answer: $9