Can someone do this for me?

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

Simplify the expression. -2/5(10+15m-20n)

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