Answer:
D.) $12n + $8u = 112 ;u = 4 + n
Step-by-step explanation:
Given that :
Cost per new books (n) = $12
Cost per used book (u) = $8
Total revenue earned = $112
store sold 4 more used books than new books
Hence,
Total revenue should be :
Revenue from new books + Revenue from used book = total revenue
Revenue from new books = $12 * n = $12n
Revenue from used books = $8 * n = $8n
$12n + $8u = 112
Number of books sold :
Number of used books sold = 4 + number of new books sold
u = 4 + n
