Of the students in a school, 20 percent are in the science club and 30 percent are in the band. If 25 percent of the students in the school are in the band but are not in the science club, what percent of the students who are in the science club are not in the band?

There are 30% of students in the band and also 25% of the students are in the band but are not in the science club, therefore the students that are in the band and also in the science club are = 30% - 25% = 5%.

20% of the students are in the science club and with the given information you know that 5 % are in the band and also in the science club, therefore the students that are in the science club and not in the band are: 20% - 5% = 15%.

Now if you read the question, it isnt asking the % of students in the school that are in the science club and not in the band (which is actually 15%) it i asking the percentage of student in the science club that are not in the band.

The total percentage students in the science club is 20% of the students in the school, and the percentage of students that arent in the band is 15%, therefore the percent of the students who are in the science club are not in the band is = 15% / 20% * 100 = 75%