1Inside the config.js of ckeditor add the following code 
2
3CKEDITOR.editorConfig = function( config ) {
4	..............
5    ..............
6    ..............
7  	config.extraPlugins = 'mathjax';
8  	config.mathJaxLib = 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-AMS_HTML';
9    ..............
10    ..............
11    ..............
12};
13
14For more details :
15
16https://ckeditor.com/docs/ckeditor4/latest/examples/mathjax.html