A Senate committee consists of 5 Republicans, 6 Democrats, and 2 Independents. A subcommittee of 3 members is randomly chosen. What is the probability that the subcommittee consists of three Republicans?

The total number of subcommittees of three members that can be formed is C(13,3) = 286

The total number of subcommittees consisting of three Republicans is C(5, 3) = 10

So....the probability is

10 / 286 = 5 / 143