Here's what I entered and got.
brian@DESKTOP-OMEN:~$ sudo apt-get install sagemath sagemath-doc-en sagemath-jupyter
[sudo] password for brian:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package sagemath
E: Unable to locate package sagemath-doc-en
E: Unable to locate package sagemath-jupyter
brian@DESKTOP-OMEN:~$ sagemath
sagemath: command not found
brian@DESKTOP-OMEN:~$ apt install wsl
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
brian@DESKTOP-OMEN:~$ apt install wsl
E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
brian@DESKTOP-OMEN:~$ sudo apt-get install sagemath sagemath-doc-en sagemath-jupyter
[sudo] password for brian:
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package sagemath
E: Unable to locate package sagemath-doc-en
E: Unable to locate package sagemath-jupyter
brian@DESKTOP-OMEN:~$
