Question 31264
I had trouble with the numbers, so I plotted expressions for 
the diagonals of each TV and the difference between them.
{{{d[1] = sqrt((x + 5)^2 + x^2)}}} and
{{{d[2] = sqrt((2.4*x)^2 + x^2)}}} are the 1st plot
{{{d[2]- d[1] = sqrt((2.4*x)^2 + x^2)- sqrt((x + 5)^2 + x^2)}}} is the 2nd plot  
If you locate y = 14 on the 2nd plot and locate  x that
corresponds to it thats the answer for the height.
It looks like about 15 

{{{ graph( 300, 500, -4, 30, -4, 30, sqrt((x+5)^2 +x^2),sqrt((2.4*x)^2 + x^2)) }}}
{{{ graph( 300, 500, -4, 30, -4, 30, - sqrt((x+5)^2 +x^2) + sqrt((2.4*x)^2 + x^2)) }}}