Question 731274
That depends on how you look at it.
Have you already taken your entree?
or are all of the 15 available for side dishes
first side dish has 15 choices
can you repeat the the side dishes?
no repeat 
then there are 14 choices for the secind
15*14=210 choices for 2 side dishes 
if all 15 are available for the first and 14 (no repeats) are available for the second