The length (L), width (W), and the diagonal (D) of the television screen make a right triangle with the legs L and W and hypotenuse D. Thus, their measurements are related through Pythagorean Theorem.
L² + W² = D²
Substituting the known values from the given,
(15 in)² + W² = (25 in)²
Solving for W in the equation gives, W = 20 in and W = -20. The second value is an extraneous root. Thus, the width of the television screen is 20 inches.