In the PS-pokerschool 5Q quiz at the end of video tutorial "playing draws"

((http://www.pokerschoolonline.com/articles/Playing-Draws-Tutorial))

the following question:

How many outs do you have holding Th, 9h, on a board of 8h, 7h, Ks, if your opponent holds As, Ad ?

The quiz states 15 outs as the correct answer. the two draws one can have. But... what about TT or 99 which would give me trips. ... what am I missing?