Plzz help really fast

Rearrange the formula c^2 = a^2 + b^2 for b

Acompany is testing in comparing to lightbulb designs the box plot shows the number of hours that each lightbulb design last before burning out which statement is best supported by the information of the plot

School has 204 sixth grade students. if the sixth grade is 30% of the total school, how many students are in the middle school?