Question

The mean of five numbers 3,7,9,12, and x is 8. Find the value of x

Answer 1

Answer:  " x = 9 "  .
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Explanation:
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To calculate the mean:
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The mean = 

     {the sum of all the values in the number set} ÷ 

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

                       →  x = 9  .
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