That is true that "positive three" would rarely be used because it means the same as just "three," but sometimes there is a reason for it to be used.
And "minus three" can be used informally instead of "negative three," but in my experience as a math teacher as well as math student, "negative three" is more often used, especially with students, because they associate "minus three" with subtraction. 2 + (-3) would nearly always be read as "two plus negative three" because "two plus minus three" can easily cause confusion to students.
I'm always confused by these math symbols [corrected spelling]
Do you have this problem only with English, or also when studying math in Chinese?
Is it mainly negative numbers that present the problem?
I used to be a math teacher (now retired). Negative numbers are often confusing to students but I had creative ways to help them understand and it was fun. (Math taught the right way can be fun, which is a big surprise to most students.)
That is interesting because there is a stereotype in the United States that Chinese people are better at math than anyone else. Because typically if there is a Chinese student in an American class, that Chinese student will be the best in the class at math. Of course, this is not really because the Chinese brain is better at math than other human brains, but because they work hard, and since with other subjects they may be slightly handicapped by language, they concentrate on the subject where language is not a barrier and excel in it through hard work.
But it is interesting to me that you say you are not good at Chinese, your own language? (I assume?) Is it just the writing, do some Chinese people find it hard to write? Of course ideographic writing looks hard to non-Chinese (although when I studied Chinese I found writing characters really fun) but we see Chinese people reading newspapers as though it were easy. And you must have a talent for languages, since you have learned English so well.
I am an educator, a retired teacher who has taught math and language arts and TESOL and other subjects, so I am very interested in the subject of how people learn, what people find hard and easy and why, and I am also very interested in the subject of educational policy. One of the main reasons I joined this page was to learn more about Chinese education. Of course I can read about this subject in many places, but this site gives me a chance to find out what ordinary Chinese people think of their education system. So please forgive me for asking those questions.