Chapter 11 - Counting Methods and Probability Theory - 11.7 Events Involving And; Conditional Probability - Exercise Set 11.7 - Page 747: 51

$\frac{2}{3}$

The probability of event B, assuming that the event A has already occurred, is called the conditional probability of B, given A. This probability is denoted by P(B|A). E: An even number, given that a yellow disk is selected. A:{3} There are 3 yellow disks. B: {2} There are two yellow disks with even numbers: 2 and 4. Thus, we have: P(B|A) = $\frac{2}{3}$