In what order should you study the books?
The right order is (Integers and Factoring can be done in parallel or any order)
1. Place Value. The Place Value system is the base for how our number system works. Without understanding it fully and deeply, there are difficulties later one with subjects that require this understanding.
2a. Integers. After whole numbers (positive integers), integers (positive and negative whole numbers), are the simplest type of numbers. However, they are not as simple as it seems, and not studying them thoroughly poses problems later on.
2b. Factoring. Factoring is a fun game, and by itself, not important. But Fractions, and some exercises in Algebra require knowing how to factor.
3. Fractions. You should not study Decimal Fractions or Percents before you fully study fractions.
4. Decimal Fractions (Decimals). Those are Fractions written with our Place Value system, the Decimal one.
5. Percents. Percents (or percentages correctly) are also fractions, but with a specific base, or a whole, made out of 100 equal parts.
The Word Problems book can and should be studied in parallel.
Note: Even if you think you only need to study Decimals, or Percents, I strongly recommend starting from the beginning with the Place Value book. You’d be surprised to discover that there are quite a number of things you thought you knew but you don’t know deeply enough, or things you didn’t know you should know.
Each book has a study plan at the beginning of the book, providing an estimated time for each section and each set of exercises.