Solve for the variable 12= -X/3???

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

Can someone check if i did this right since i really want to make sure it’s correct. if you do you so much

Which graph represents the equation y =4x