The player wins if he rolls a 4 on the number cube.
Total number of outcomes on number cube = {1,2,3,4,5,6}
Probability of winning =

If the number cube is rolled 24 times.
Therefore, the reasonable prediction for the number of successful rolls
=

= 4.
Therefore, the reasonable prediction for the number of unsuccessful rolls
= Number of times number cube rolled - reasonable prediction for the number of successful rolls
= 24 - 4
= 20.
Therefore, the reasonable prediction for the number of unsuccessful rolls is 20.