Help about solving broken packages on my desktop

[慕冬亮]

Hello guys,

I am writing to kindly ask for some help about solving broken packages
on my desktop. I have updated and upgraded the whole system.

```
$ sudo apt update && sudo apt upgrade
Hit:1 http://mirrors.hust.edu.cn/ubuntu focal InRelease
Hit:2 http://mirrors.hust.edu.cn/ubuntu focal-updates InRelease
Hit:3 http://mirrors.hust.edu.cn/ubuntu focal-backports InRelease
Hit:4 http://mirrors.hust.edu.cn/ubuntu focal-security InRelease
......
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
```
```
$ sudo apt-get install build-essential python3-dev libssl-dev
inotify-tools python3-dbus
......
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 build-essential : Depends: libc6-dev but it is not going to be installed or
                            libc-dev
                   Depends: gcc (>= 4:9.2) but it is not going to be installed
                   Depends: g++ (>= 4:9.2) but it is not going to be installed
                   Depends: dpkg-dev (>= 1.17.11) but it is not going
to be installed
 libssl-dev : Depends: libssl1.1 (= 1.1.1c-1ubuntu4) but
1.1.1f-1ubuntu2 is to be installed
 python3-dev : Depends: python3 (= 3.7.5-1ubuntu1) but 3.8.2-0ubuntu2
is to be installed
               Depends: libpython3-dev (= 3.7.5-1ubuntu1) but it is
not going to be installed
               Depends: python3.7-dev (>= 3.7.5-1~) but it is not
going to be installed
E: Unable to correct problems, you have held broken packages.
```
```
$ sudo apt install gnome-shell-extensions
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 gnome-shell-extensions : Depends: gnome-shell (< 3.35) but
3.36.4-1ubuntu1~20.04.2 is to be installed
E: Unable to correct problems, you have held broken packages.
```
--
My best regards to you.

     No System Is Safe!
     Dongliang Mu