I feel your pain. I, too, have always struggled with algebra. And I know what you mean about sample problems not matching the exercises. I had that same issue when I was taking algebra in college. I actually failed pre-algebra twice (squeaked by with a C the third time around), failed beginning algebra twice (squeaked by with C third time around), failed intermediate algebra twice (squeaked by with a C third time around). I passed college algebra the first time around because I hired a math tutor at $25 an hour. Fast forward in time, and I have to study for the GRE, which required me to relearn all the algebra. Here's what I did.
I picked up this book:https://www.amazon.com/Beginning-Algebra-Margaret-L-Lial/dp/0321127110/ref=pd_bxgy_14_2?_encoding=UTF8&pd_rd_i=032112711…
Beginning algebra is the equivalent to Algebra 1 in high school. However, this book takes you step by step by the hand, explains things clearly and thoroughly. The sample problems will even direct you to the actual exercise #s that it is representing. Take the time to write very careful notes, and work out the sample problems yourself, following directions provided. There are often 7-10 pages of sample problems followed by a plethora of exercises and real world problems. There is an answer key in the back of the book for all odd questions. Admittedly this is time-consuming, but it works. Find every video you can to help you with specific algebraic concepts, such as factoring binomials.
Also, pick up the Solutions Manual. This way, when you know you got # 27 wrong, you can look up the solution to see WHY you got it wrong and learn from your mistakes. Student Solutions Manual for Beginning Algebra: Margaret L. Lial, John Hornsby, Terry McGinnis: 9780321444714: Amazon.co…
I wish the books were this good when I was taking the classes for credit! I also arranged to "sit in" on a colleague's class who was teaching beginning algebra. Since I wasn't taking the course for credit, I wasn't required to take any tests or do any homework, but I did anyway. I was getting 100's on my tests. This was the first time I had ever seen an A on a math test since I was 12!!
I also just found this. I don't know how helpful it is, but it may help you. If you really feel that you need pre-algebra before being able to understand algebra 1, this site has it. https://www.mathplanet.com/about-mathplanet
Prealgebra at Cool math .com: Free Pre-Algebra Lessons and Practice Problems
Good luck to you. You can do this.