According to your answers, it looks like you have a solid foundation in math, however, you missed this one problem. The vertical lines in that last problem means "Absolute Value." You should ignore the negative and positive signs of each number and then add the numbers together. If everything has been easy up to this point, then you can start with volume 5 of the Learn Math Fast System.
RESULTS: The 9th Grade Level, however, the Learn Math Fast System is for all ages. Volume 5 covers 9th - 10th grade algebra, but there is no mention of grade level within the books.