The prompt student@ubuntu:~$ is the shell's hint about where you are working.
Before any change, an administrator finds out three things: which name they are working under, on which machine, and in which directory. Mix up the machine or the directory, and the change lands in the wrong place.
Three commands and the prompt
Run the three commands and find what each one prints in the prompt student@ubuntu:~$.
First, predict
The prompt ends in ~$. What will pwd print?
Now start the exercise, run the command and compare your prediction with the output.