A is the initials of Antwerp, Germany. Pay attention to capitalization.
2. The answer is the same as the solution. Please refer to my answer 1.
3. When demonstrating logical relations, you don't need to specify related words such as "known", you can->; This symbol replaces it.
Description in Chinese: A>b, B > C, so A>C
In Germany, math tests can be written as: A>b and B > C = & gtA & gtC.
German schools have no strict requirements on the format of China's mathematical demonstration.
If you want to see more questions about German mathematics, you can search for the keyword "matematic losung" in Google Germany. You will find many math problems marked with answers. Read more books and you will know how to write.