Taks practice math question 8th grade?

Well, from what I gather, there are a total of 35 people in music. The fact that 20 are in both band and orchestra seems kind of irrelevant. So you subtract 15 from the total of 35 because that many students ARE in chorus. So 20 out of 35 are not in chorus. Divide them both by the greatest common denominator of 5, which makes it 4 out of 7. 4/7 is 0.571428571. That is what I got based on the information you gave me. Hope it helps.