Intermediate Algebra by AoPS
Intermediate Algebra is an AoPS book. This book is written by Richard Rusczyk and Matthew Crawford.
Crawford is the founder and CEO of MIST Academy, as well as the first employee at AoPS. He scored perfect on the National MathCounts written test in 7th grade and achieved second place in 8th grade. Crawford achieved a perfect score on the AIME in grade 9, and was invited to the Mathematical Olympiad Summer Program three times. He was part of the top four Putnam and is the youngest winner of the National Mu Alpha Theta convention, as well as being the only five-time winner of the Alabama State Written Examination. He achieved high scores on the ARML twice and won the Zachary Sobol Award.
Crawford was also the author of Introduction to Number Theory by AoPS.
Rusczyk is the founder of AoPS. He achieved perfect scores in AIME, won the USAMO, and participated in the Math Olympiad Summer Program. Along with this, Rusczyk has been a co-author of Art of Problem Solving: Volumes 1 & 2, Introduction to Prealgebra, and Intermediate Algebra by AoPS.
Rusczyk was the author of Introduction to Algebra and Introduction to Precalculus by AoPS.
The difficulty rating of Intermediate Algebra by AoPS varies from 2.5-7 depending on the Chapter (see artofproblemsolving.com/wiki/index.php/AoPS_Wiki:Competition_ratings).