How to remove 1 partition

When I created partitions on my passport for Mac drive, I accidentally created 3 partitions instead of 2 - can I remove/delete one partition and add that space to one of the other 2 partitions? Or do I need to reformat the whole drive? Thank you for any comments.

Yes, you can deleted the unwanted partition via Disk Utility. However, if you are unable to merge the spaces then only you can reformat the entire hard drive. Do backup before taking any action.

I tried to delete the partition without any success - what are the steps to do this? thx.
Also, do you mean back up to a different drive first?