In an older television set, the screen height is 0.75 times the screen width. if a television set measures 20 inches along the diagonal, what is the screen width?

The television set has a rectangular shape. The diagonal of this rectangle along with its width and length together form a right angular triangle.
This means that we can apply the Pythagorean theorem which states that:
(diagonal)^2 = (length)^2 + (width)^2

Let the width be w. We know that the length is 0.75 times the width, this means that: length = 0.75 w

Substitute in the above equation:
(20)^2 = (0.75w)^2 + (w)^2
400 = 0.5625 w^2 + w^2
400 = 1.5625 w^2
w^2 = 256
w = 16

This means that the width of the screen is 16 in.