Contingency Tables · Exercise 17

Use the information in the to answer the next eight exercises. The table shows the political party affiliation of each of 67 members of the U.S. Senate in June 2012, and when they would next be up for reelection.
$$\begin{array}{ccccc}\text{Up for Reelection:}& \text{Democratic Party}& \text{Republican Party}& \text{Other}& \text{Total}\\ \text{November 2014}& \text{20}& \text{13}& \text{0}& \\ \text{November 2016}& \text{10}& \text{24}& \text{0}& \\ \text{Total}& & & & \end{array}$$

Suppose that a member of the U.S. Senate is randomly selected. What is the probability that the senator was up for reelection in November 2014, knowing that this senator was a Republican?

Its source prints no answer for this problem, so there's nothing to check against.

OpenStax, Statistics · §3.4 Contingency Tables · Exercise 17