He had 5 left. Nina had 14 seashells. That was 5 more than Pedro had. As children talk about mathematics, it is important to keep in mind that what appears at first to be an incorrect response may be, in fact, an inability to communicate. Of primary importance is the value children derive from reflecting on their responses.
Writing is a communication skill that has been used too infrequently in mathematics.
It is particularly useful because it allows a child who is uncomfortable in oral situations to express understanding in a less public forum. After children have solved a problem, they can write their answer in sentence form, which helps them exhibit a knowledge of the problem's place in the real world and clarify their thinking. Students can write a letter to tell a friend about something they have learned in mathematics class. This type of activity allows the students to consider mathematics for a new purpose. If letters are exchanged, then students learn from the thought processes of their peers.