Question

The screen on your old television is 20 inches wide and 15 inches high. The owners are downsizing using the scale factor 4/5 what are the new width and the height of the new television?

Answer 1

Well, 1/5 would mean dividing both width and height by 5. Do that... then times new answer by 4 to get 4/5. 
So...

20/5 = 4*4 = 16 in wide
15/5 = 3*4 = 12 in high

Hope this helps! :)