Both the pages are simple and elgeant.
They are easily understandbale.
Operations such as Subtraction, Division with variables can also be explained.

MathsIsFun, they seem very accessible to me.  I could only comment on things to add, but you stated above that you plan on doing such anyway.  I would suggest that before you move to more complicated material in algebra, a little chat on order of operations would be critical.  We tend to follow those rules without thought at this point in our lives, but for those new to algebra it is paramount to know them.

  Order of operations popped into my head while reading the pages because they weren't needed.  Anyway, I thought then that it would not be so apparent to a newcomer and also low on our natural list of things to explain. (Because we usually don't really think about it anymore.)

I also think they're well done.

While you're treating order of operations, a bit on the distributive property would also be beneficial to the multiplication page, since it's not readily apparent at first that if you multiply both sides by something, you have to do it to everything on both sides.

I remember having a tough time with the distributive property in 7th grade. Surprisingly, a simple, clear explanation of this concept was not available to me. It seemed like this mysterious thing with a fancy name instead of the simple, intuitive concept that it is.

But I can't understand nothing-it's too complicated!