Your hand-writing isn't the worst I've seen, by far. I actually see a lot of words in there with which I like, as far as the hand-writing is involved.
As pointed in the post above, try not to mix up your upper- and lower-case letters. It's nicer on the eyes when there a smooth flow as far as how the words look. If you want to write it all in caps, that's totally fine. A good example is when you wrote "numbers" and "decimals" in the middle; it looks very consistent and has a nice "flow" to it. In contrast, when you wrote "adding" at the top the letter "g" at the end kind of throws it off because there's such a large height difference compared to if the "g" were written a bit lower to the height of the "in."
Secondly, consider the spacing between letters. Try to keep it as consistent as you can. When you wrote "irrational numbers" in the middle, I had to re-read it a few times to make sure it wasn't supposed to be "I rrotional" or something. Also, when you wrote "imaginary numbers" there were quite a few spacing differences between the "g-i-n" and the "a-r-y."