Yes, you can.
First you back up the data that are on the partition.
Click on the "Disk Management" option from the menu on the left-hand side.
Select the partition you want to merge, and left-click on it.
Select the "Delete Volume..." option and confirm that you wish to erase all of the data. Make sure you are on the right partition, double check.
Select the partition you wanted to merge, and right-click on it, selecting "Extend Volume..." and click "Apply".
The partitions will now be merged.