Height of window 0.6 feet less than 2.5 times it width height of window 4.9 feet

Suggest you use some punctuation here:  "The height of window is 0.6 feet less than 2.5 times it width.  The height of window  is 4.9 feet.  Find the width of the window."

height of window = 4.9 feet = 2.5(width) - 0.6 feet.

simplify this equation by adding 0.6 feet to both sides of the equation:

4.9 feet + 0.6 feet = 2.5 (width); find width:

5.5 feet = 2.5 (width)

Dividing both sides of this equation by 2.5 will result in an equation for the width of the window, in feet.