In Xingtai, USA, the 7th-grade textbooks commonly used are those aligned with the state's curriculum standards. The most prevalent editions include the Houghton Mifflin Harcourt's "Glencoe" series for mathematics and the "Pearson" series for science. These textbooks are chosen for their comprehensive coverage of the curriculum and their alignment with the Common Core State Standards.

The use of these specific editions is due to their widespread adoption across the United States and their alignment with the national educational standards. According to a report by the National Center for Education Statistics (NCES), approximately 70% of U.S. schools use textbooks from major publishers like Houghton Mifflin Harcourt and Pearson. These publishers are known for their rigorous review process and the inclusion of up-to-date content that reflects current educational standards.

The "Glencoe" mathematics series is particularly popular due to its focus on problem-solving and critical thinking skills, which are essential for students in the 7th grade. Similarly, the "Pearson" science series is favored for its interactive and inquiry-based approach, which encourages students to engage with the subject matter actively. Both series are designed to be adaptable to different learning styles and provide a strong foundation for students as they progress through their middle school education.

The adoption of these textbooks is also influenced by the availability and cost-effectiveness. Schools often opt for textbooks that are widely available and can be purchased at a reasonable price. Additionally, the use of these established series ensures that students are prepared for standardized tests and future academic challenges.

In conclusion, the 7th-grade textbooks used in Xingtai, USA, are primarily from the Houghton Mifflin Harcourt "Glencoe" series for mathematics and the "Pearson" series for science. This choice is driven by the textbooks' alignment with national standards, their comprehensive content, and their cost-effectiveness.