Question 1138954
Let one of the number be {{{ x }}} 
{{{ f(x) = x*( 28 -  x )}}}
{{{ f(x) = -x^2 + 28x }}}
{{{ x[max] = -28/(2*(-1)) }}}
{{{ x[max] = 14 }}}
and 
{{{ 28 - x = 14 }}}
Both numbers are 14
check:
Here's the plot:
{{{ graph( 400, 400, -20, 30, -20, 200, -x^2 + 28x ) }}}