I know there are many questions about this topic, but I could not find an answer to my particular case. I have a dual-boot configuration on my 500 GB single hard drive, and I needed to add some space to my Ubuntu.
I have freed 7292 MB of space inside Windows in order to fix that, but now I am in the condition of being unable to add that space to Ubuntu (40 GiB partition), even if the free space appears to be adjacent to my root partition.
Here's a screenshot of my hard disk situation:
How do I add the free space to my Ubuntu partition?