Probability of choosing hearts = 13/52 = 1/4 (13 hearts and total 52 cards)
Probability of rolling a 2 in a number cube = 1/6 (6 faces containing 6 different numbers and one face containing a 2, simply think of dice)
Probability of choosing heart and rolling a 2 = 1/4 * 1/6 = 1/24