How can I remove Ubuntu 15.10 from a multiboot computer with windows 10 Ubuntu Kylin and Deepin 2014.3?
You remove an OS from within another OS. How you do that from Windows or from Deepin is off topic.
From Ubuntu Kylin: start gParted, select the partitions with Ubuntu and delete them. Mind to check twice before you delete it that it is the correct one you delete. I have no idea what Deepin has as a description inside gParted but your Ubuntu 15.10 will be named actually "Ubuntu 15.10". If you need the actual partitions the easiest way is to boot up 15.10 and check
df -h or
more /etc/fstab. Mind also that if you shared partitions between the OS's to not remove that one.