Naomi has 18 lilies in her garden. Yesterday 1/2 of them bloomed, and today, 2/3 of the remaining lilies bloomed. How many lilies have not yet bloomed?

Assuming that Naomi has 18 lillies totally, (including those that haven't bloomed):

Yesterday 1/2 * 18 = 9 bloomed.

That leaves 18 - 9 = 9 not yet bloomed yesterday.

Of those 9, 2/3 of them bloomed today.

so 2/3 * 9 = 6 bloomed today.

9 + 6 = 15 have bloomed in total then.

18 - 15 = 3

3 lilies have not bloomed yet.

18 divide by 2 = 9 9 divided by 3 x2 = 6 9-6=3 that haven't bloomed