Answer:
The answer is a. 320 books
Explanation:
Hi
first of all, we can see "discount shelf for 70% off the regular price." is irrelevant info and a distraction, so we can use the info "If 2/3 of the books sold" then
![BSold=(2)/(3) *960=640](https://img.qammunity.org/2020/formulas/mathematics/college/bs13zosss3awc7a82u62lmtd5lj7vwgipj.png)
Now we can find the number of books remaining on the discount shelf
![BRemaining=960-640=320](https://img.qammunity.org/2020/formulas/mathematics/college/5s2yiqvvux86kkwcu9kofwjhp2j5lhn99c.png)