Nafis, A. M. A.; Herumurti, D. EFFECTIVENESS STUDIES OF THE LEARNING BASIC MATHEMATICAL OPERATIONS ON USERS USING EDUCATION GAMES WITH ESCALATING DIFFICULTY LEVEL IN SEVERAL TYPES OF GAMES. JUTI 2020, 18 (2), 115-124. https://doi.org/10.12962/j24068535.v18i2.a989.