Answer:
17
Step-by-step explanation:
Let x be the number of books and y the number of CDs,
[tex]x+y=25\\[/tex]
The prices of the products are multiplied with the quantity bought, therefore:
[tex]1.5x + 5y = 65.50[/tex]
Multiplying the first equation by -5, then multiplying the two equations:
[tex]-3.5x=-59.5\\x=17[/tex]
