Question 1203764
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The solution by @josgarithmetic, giving the answer 13, 15, 17, is INCORRECT.


The correct answer is -13, -11, -9.


<pre>
                     <U>Solution</U>


Let the numbers be  n, n+2, n+4.


Write an equation as you read the problem

    {2(n+(n+2)) = 3(n+4)-21


Simplify and find n


    2(2n+2) = 3n+12-21

    4n + 4 = 3n - 9

    4n - 3n = -9 - 4

       n    =   -13.
</pre>

Solved (correctly)