If we take a look, we could say that
For the first selected new board member, we have 15 options
for the second one, we have 14 options (because one of the persons was already chosen)
for the third one we have 13 option, 4th one 12 options and 5th one 11 options
So to get the number of different boards we need to multiply the options for each one, so:
15*14*13*12*11= 360360
now we need to divide for the number of member of the board that need to be chosen so
5*4*3*2*1
So the different boards are:
3003 different boards could be formed