3. In the store, apples were sold. On the second day, they sold a quarter of the amount of apples sold on the first day, and an additional eight kilograms. On the third day, they sold a quarter of the amount of apples sold on the second day, and an additional eight kilograms. How many kilograms of apples were sold on the first day if 18 kilograms were sold on the third day?
Solution. Let's reason from the end. On the third day, 18 kg of apples were sold. If we subtract 8 kilograms, the remaining 10 kg will be a quarter of the amount sold on the second day. Therefore, 40 kilograms of apples were sold on the second day. Of these, 32 kilograms are a quarter of the amount sold on the first day. Therefore, 128 kilograms of apples were sold on the first day.

Answer. 128 kilograms.