How do you find out if an equation is linear or nonlinear?

The median of a data set is the measure of center that is found by adding the data values and dividing the total by the number of data values that is the value that occurs with the greatest frequency that is the value midway between the maximum and minimum values in the original data set that is the middle value when the original data values are arranged in order of increasing (or decreasing) magnitude

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

Rewrite 9 log, x2 in a form that does not use exponents. 9log, x = log, x