The graph compares the scores earned by 100 students on a pre-test and a post-test. Two box and whisker plots showing Pre-Test and Post-Test scores on a number line from 0 to 100. The upper plot represents the pre-test scores. For this upper plot, the minimum number is 0, the maximum number is 78, the right side of the box is 60, the left side of the box is 16, and the bar in the box is at 30. The lower plot represents the post-test scores. For this lower plot, the minimum number is 4, the maximum number is 100, the right side of the box is 83, the left side of the box is 30, and the bar in the box is at 45.

About how many more students scored greater than 30% on the post-test than on the pre-test?

15