My answer to a question on Quora: Is it normal that one doesn’t understand a math procedure unless demonstrated by a teacher? Like for example, I cannot grasp what the textbook is trying to say but if I watch a video tutorial on how a procedure is done, I can understand right away.
Today I attended a seminar of mathematics education experts. They are seeing inability of many students to adequately understand written/printed texts as a serious and growing problem facing school mathematics education. Mathematical texts are difficult. What are other (that is, non-mathematical) difficult texts that you have read in your life? For example, have you ever tried to read fine print in an insurance policy? By complexity, this could easily beat maths textbooks. Ability to read and understand a difficult text is a useful skill — a skill for life.