If u know the answer, please help me

Write the system of equations represented by the matrix. 0 1 2 4 -2 3 6 9 1 0 1 3

Which number produces a rationale number when multiplied by 1/5

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