Answer=210 ways
Okay. I'm not entirely sure this is the BEST way to solve for this answer, but nonetheless, I'll show how I would solve the equation.
First, lets look at the probability of the two options happening. The probability of one of the 15 members becoming president is 1/15. Then, since one student is already being used for the spot of president, the odds of another student becoming vice president is 1/14.
From this, we know that there are 210 options for the positions of president and vice president total (since 210 represents the whole).
So they can choose the president and vice president 210 different ways