7/8 times and 3/5 times are expressed in the form of ratio, and the difference in the number of copies of the two books is also expressed in the form of ratio.

Original storybook: original science and technology book: the difference between the original two books = 7: 8: 1

Now Storybook: Now Science and Technology Book: The difference between the two books = 3: 5: 2.

But 220 books have been lent out, and their differences will not change. Therefore, the "difference" in the above two groups is converted into 2.

Original storybook: original science and technology book: the original difference between the two books = 7: 8:1=14:16: 2.

Now Storybook: Now Science and Technology Book: The difference between the two books = 3: 5: 2.

It is not difficult to see that the above two books are less than story books and science books 1 1 (that is, 220 books borrowed), so dividing 220 by 1 1 equals 20 books (20 books each). The original science and technology book was 16. 20 times 16 equals 320 copies.

I hope I can help you.