The surface of the TV is depicted in the diagram below.
Then, according to the Pythagoras theorem.

And, according to the problem

We have two equations and two unknowns; therefore, we can solve the system.

Solve the quadratic equation as shown below

But h is the height; thus, it has to be a positive quantity. Then, h=10
Finally, we need to find l

The answers are: height equal to 10 and length equal to 24.