Use 1: 100 to conveert to the real world

How can you decide witch operations to use to slice a two step equation

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

The difference between two numbers is one. three times the larger number minus two times the smaller number is 9. what are the two numbers