This app is surprisingly extensive for a free version as it offers quite an amazing variety of tutorial videos. Unfortuantely, it gives no practice material. That is where the app wants you to pay $4.99 for each lesson. So this app is outstanding for improving conceptual understanding of algebra and geometry, but non-existent in increasing knowledge through practice.
Common Core State Standards:
Various Tutorial videos that prepare students for concepts from middle school to high school to community college level Algebra and Geometry.
Analysis of Change
Variables & Expressions
various algebra tutorial videos