To answer this question, we need to find the maximum and minimum values in the stem-and-leaf plot.
The most pages Omar read in a day is represented by the stem 3 with a leaf of 4, which equals 34.
The least pages Omar read in a day is represented by the stem 2 with a leaf of 2, which equals 22.
The difference between these two values is 34 - 22 = 12.
So, the difference between the most pages Omar read in a day and the least pages he read in a day is 12.