Chapter 11 - Counting Methods and Probability Theory - 11.3 Combinations - Exercise Set 11.3 - Page 707: 34

3.066 x $10^{19}$

The number of possible combinations if r items are taken from n items is nCr = $\frac{n!}{r!(n-r)!}$ The number of ways to select Senate members for a Foreign Relations committee is 100C18= $\frac{100!}{18!(100-18)!}$ = $\frac{100!}{18!82!}$ = 3.066 x $10^{19}$ ways