We have been given that there are total 120 books on Raymond's bookshelf that he has not read. Further, we know that he plans on reading 3 books per week until there are only 24 unread books are left.
Let us say Raymond reads the books for w weeks. Since he reads 3 books per week, therefore, he would have read 3w books in w weeks.
Now that Raymond has read 3w books out of total 120 unread books, the remaining unread books can be found by subtracting 3w from 120 as shown below:
[tex]120-3w=24[/tex]
Now, in order to find the number of weeks, we will solve this linear equation for w.
[tex]3w=120-24=96[/tex]
[tex]w=\frac{96}{3}=32[/tex]
Therefore, the required equation is [tex]120-3w=24[/tex] and it will take Raymond 32 weeks before he has read enough books to have left with just 24 unread books.
Thus, the correct answer is option (A).