Or you could just Flip Vertical for the first example, or Flip Horizontal for the 2nd.
Enable the Selection tool, look on the control bar (3rd horizontal bar from the top) for these icons/buttons:
Flip Horizontal
(6th from left)
Flip Vertical
(7th from left)
These commands will not place the objects relative to the axis, they just flip the object. So you'll have to find some kind of technique to place them properly. There are many ways to place objects precisely, and your choice which way depends on the specific circumstances on the canvas, along with your own preference.
We can give you some ideas about how to do that. But I'm not sure if your examples are coming from your project, or if you just made them for examples. So let us know if you need help with placement (and be sure to show example from your project).
You know, Inkscape really should have a way to that automatically. I'm tempted to post a feature request.....
(although I wouldn't be surprised if there already is a request....)