Final answer:
To calculate the number of students in each grade, multiply the given percentage by the total number of students in the school band.
Step-by-step explanation:
The number of 6th, 7th, and 8th graders in the school band can be calculated based on the given percentages. To calculate the number of students in each grade, you can multiply the given percentage by the total number of students in the school band. For example, if the percentage of 6th graders is 30% and the total number of students in the school band is 100, you would calculate it as follows: 30% * 100 = 30 6th graders.