A two-digit number means that this number consists of two numbers, but it has only one digit and ten digits. For example, 12, 35, 98 and so on are all two digits. For example, 05 and 352 are not two digits, and 352 is three digits.
The number of digits of a natural number is called the number of digits. One digit is one digit, and two digits are two digits. The maximum digit is 9, the minimum digit is 1, the maximum digit is 99, and the minimum digit is 10.
Mathematics is a universal means for human beings to strictly describe and deduce the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence. In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics.
How to learn math well
Develop the habit of previewing. This is a good way for me to study mathematics for many years, because I know what I can't do by learning what the teacher should say first in advance, and I have a focus when I study. Of course, it would be better if you taught yourself completely.
Follow the book to do exercises. Preview is not an end. If you have time, you can do examples and exercises after class and check the preview. If you can explain everything, you can learn it. Even if you can't, you can listen to the teacher again.