Add Below code in these paths: Themes/themeone/views/common/editor.blade.php
: Themes/default/views/common/editor.blade.php
<script type=”text/javascript”>
CKEDITOR.config.extraPlugins = ‘mathjax’
CKEDITOR.config.mathJaxLib = ‘//cdn.mathjax.org/mathjax/2.6-latest/MathJax.js?config=TeX-AMS_HTML’
</script>