running out of room in root

[Michael]

I am getting an error: File system Root only has 143.6 MB remaining.
What should I do
michael at MyNUC:~$ df / -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda5        28G   26G  137M 100% /
michael at MyNUC:~$

-- 
:-)~MIKE~(-: