Unavailable free space on hard drive
I recently noticed that my new MacBook Pro was running low on available storage space. It has a 250 GB fusion drive with a 75Gb partition for Windows. When I looked at the drive in Disk Utility, I found an extra partition of 58 GBs that is labeled "Free Space". I have no idea how the extra partition came to be.
I have tried to delete the partition with no luck. I get this error message:
How do I delete the "Free Space" partition and add the space to the Macintosh HD partition? By the way the "untitled" partition is Windows on Bootcamp.
iMac, OS X El Capitan (10.11.2)