Since these notebooks are distributed to seven children on average, there are only six left, which means that 1 book is exactly a multiple of 7. The average distribution of 9 children will leave 8 books, which means that adding 1 book is exactly a multiple of 9. That is to say, the number of these notebooks plus 1 is the common multiple of 7 and 9, and the condition of "at least" in the problem shows that the number of these notebooks plus 1 is the least common multiple of 7 and 9, and the least common multiple of 7 and 9 is 7×9, so the column equation is solved as follows:

Solution: Suppose there are X notebooks.

X+ 1=7×9

X+ 1=63

X=63- 1

X=62

A: There are at least 62 notebooks.