Grade three students don't understand the equation, so it can be calculated as follows:

According to the meaning of the question: Mingming is not convinced, take half by himself, and Dongdong takes back half from Mingming-Dongdong must move books in multiples of 4.

(One ***26 copies) The multiples of 4 within 26 are only 4,8, 12,16,20,24. Starting from 4, it is eliminated one by one by substitution method, and it is known as 16.

For example, suppose Dongdong robbed eight books first, but Dong Yao was unconvinced and robbed half of four books. Dongdong snatched back half of two books from Yao Ming. At this time, Dongdong refused to take six books, but Dong Yao refused and Dongdong returned five books to him. At this time, Dongdong 1 book, 7 books in Yao Ming. ....

Suppose Dongdong robbed 12 books first, but obviously he was not convinced, so he robbed half of six books, and Dongdong snatched back half of three books from Mingming. Dongdong refused to give him five books at this time, and then Dongdong took four books, obviously taking eight. ....