Abstract
"Ratiber und Goldschatz" (Thief and Treasure) is a learning environment in an innovative german mathematics textbook, Das Zahlenbuch, which was edited by E. Ch. Wittmann and others. I developed the mathematical lesson of negative numbers for 7th grade students which is based on "Railber und Goldschatz". In this paper, I analyzed the students activities of the lesson and reported the results. In the lesson, the most of the students learned activity and can answer the questions like "-2+3, 4-6 etc".
