Selecting verious Rows and columns in numbers on mac

Enter the first empty column you want to select.
Command-Shift right or left depending on where the other empty columns are relative to your selected cell. Usually, extra columns are to the right.
VO-Shift-M and select Delete Columns.
If this command doesn't appear in the context menu, select it from the Table menu.

1. Vo-|.
2. Vo-up or down to choose row or column reference tab and vo-space.
3. vo-space on the tab to select.
4. option-command-delete to delete a selected row and control-command-delete to delete a selected column.

There is a list of Numbers keyboard shortcuts that is accessed from the help menu.