There were seven boxes. In some of them, seven more boxes (not nested inside each other) were placed, and so on. In the end, there were 10 non-empty boxes.

How many boxes are there in total?
At each operation, one empty box is filled. Since there are now 10 non-empty boxes, 10 operations have been performed. With each operation, seven boxes were added. Therefore, in the end, there are $7+10 \cdot 7=77$ boxes.