Answer
Probability = $\frac{3}{100}$
Work Step by Step
Total ways to select 3 winners out of 100 = $C$(100,3) = 161700
Ways in which Michelle is one of the 3 winners = $C$(1,1)$\times$$C$(99,2) = 4851
Probability = $\frac{4851}{161700}$ = $\frac{3}{100}$