Q: i have a folder on my iPhone called "photos from my mac" and when i try to delete them they won't delete. how do i get rid of them?

On your Mac - go to itunes and DE-select that album from the syncing of your photos.  Then sync your phone.

Those were added by syncing from iTunes and need to be deleted by syncing again using the instructions quoted below from Sync photos to your iPhone, iPad, and iPod touch in iTunes - Apple Support

Delete synced photos

1. In iTunes, locate and click on your device.
2. Click Photos.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.

Learn how to delete photos and video synced from iTunes when you can't access the originals.

If you don't have any photos from your Mac that you want to keep on the phone then try the option shown in the link of :

To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."

The other possibility is that the album is no longer on your Mac. In that case follow the instructions in Delete photos and video synced from iTunes when you can’t access the originals - Apple Support