I'm stuck on backing out of bullets

[nrsmd]

My presentation has bullets, fairly normal, and sub-bullets, fairly normal. I can't figure out how to move back from the sub-bullet to the bullett, to the main heading.

Once in in the bullet field, each time I hit enter or backspace, I can't go back.

I am new with this, so I assume it's fairly simple.

xxxxxxxxxxxxxxxxxx
o. bbbbbbbbbbbbb


o. ccccccccccccccc
a. mmmmmmmmmm
b. rrrrrrrrrrrrrrrrrrrrrr

Now, after the last r above, How do I go back one step at a time to get to the o. level or to the X level?????