I know to water 15 saplings: Xiaohong said that she watered 8 saplings.

Question to be solved: How many trees are not watered?

The answer can be as follows: 15-8=7.

There are still seven trees that are not watered.

"Xiaoli says there are six people here" is an unnecessary condition, which deliberately interferes with students' problem solving. Check whether we can choose useful information from it and answer questions with interrelated information.