$ sudo apt-get update
$ sudo apt-get install libjs-mathjax 

libjs-mathjax is installed in your system.

Make ensure the libjs-mathjax package were installed using the commands given below,

$ sudo dpkg-query -l | grep libjs-mathjax *

You will get with libjs-mathjax package name, version, architecture and description in a table

libjs-mathjax package basic information: