Websites, apps, and manipulatives to master pre-algebra.

Free interactive illustrated resource organized by topic.

Mathigon is a free interactive math manipulatives site for basic, pre-algebra, algebra, geometry...

MathUpgrade from Learning Upgrade

Math App - Grades K - 8  - Pre-Algebra - Algebra - High School Equivalency

Geogebra  - Free geometry and algebra tools. 

Virtual Nerd - Pre-Algebra is a free website with colorful visual explanations by topic.

Toy Theater

Hundreds of colorful interactive math visualization tools. Link