Answer: " x = 9 " . ____________________________________ Explanation: ____________________________________ To calculate the mean: ____________________________________ The mean =
{the sum of all the values in the number set} ÷
{the number of values in the data set} ; ____________________________________ To solve for "x" ; ____________________________________ Given that the "mean" is: "8" ; ____________________________________ 8 = { 3 + 7 + 9 + 12 + x } / 5 ; ____________________________________ ↔ { 3 + 7 + 9 + 12 + x } / 5 = 8 ; ____________________________________ → { 3 + 7 + 9 + 12 + x } = 8 * 5 ; ____________________________________ → { 31 + x } = 40 ; ____________________________________ ↔ x + 31 = 40 ; ____________________________________ Subtract "31" from EACH SIDE of the equation; to isolate "x" on one side of the equation; and to solve for "x" ; ____________________________________ → x + 31 − 31 = 40 − 31 ;
