84. At the meeting, there are 100 people present. In how many ways can a presidium of the meeting be elected, consisting of a chairman, a secretary, and seven other members of the presidium?
84. Answer. $A_{100}^{2} \cdot C_{98}^{7}=S_{100}^{7} \cdot A_{93}^{2}=S_{100}^{9} \cdot A_{99}^{2}$.