I would leave them alone. You may have other software packages (including some Microsoft apps!) that still use the earlier versions.
For the small amount of disk space you would free up, it’s not worth the bother of trying to sort out exactly what you need and what you don’t.
Maybe the other “2015” one from March is the 32-bit version, which still be needed for some other software - just guessing!
If you REALLY want to get rid of them, don’t delete them, rename them (and write down exactly what you did!) so you can easily restore them if something else goes unstable.