trouble selecting mono

Hi, I am trying to remove the vocals from a song. I split the stereo track and inverted the bottom one. When I go to click on the dropdown and change both tracks to mono it does not offer that as an option. How do I change both tracks to mono? I am using Windows 7 and Audacity 2.2.1.

Ignore out of date tutorials scattered around the internet.
See here in the manual: Tutorial - Vocal Removal and Isolation - Audacity Manual

I am running Windows 10 and Audacity 2.2.2
Trying to remove vocals from a track.
After I split the stereo track, and invert the right channel, I am not able to use the pulldown menu to convert each track to mono.
The feature is just not there, although I watched a video on YouTube where the full complement of features was in the pulldown menu.
So my question is how do I get the menu to show up?

Ignore out of date tutorials scattered around the internet.
See here in the manual: Tutorial - Vocal Removal and Isolation - Audacity Manual