Understanding the relationship between expressions that aren't equal.
Kumon Algebra 6-8 (typically Level H in the new numbering system, or levels 6-8 in older booklets) covers: Kumon Algebra 6-8 Answer Key
Breaking down expressions into their simplest forms. Grades 6-8: 9781941082584 - Christianbook.com
To help you understand what you are dealing with, here are three typical problems from this level. Solve them yourself to see if you even need an answer key. Kumon Algebra 6-8 Answer Key
The workbook includes a complete answer key at the back of the book: Algebra, Grades 6-8: 9781941082584 - Christianbook.com