Gabriella wants to tile a room with an area of 320 square feet. the width of the room is 4/5 its length. what are tge length and width of the room?

Area = length x width
But width = 4/5 x length
so 320 = length x 4/5length
Rearranged, 320 = 4/5(length)(length)
length x length = length^2
Divide both sides by 4/5
400 = (length)^2
Square root both sides
20 = length

So now you know the length, you can calculate the width. 
Width = 4/5 x length
= 4/5 x 20
= 16

Length = 20ft, Width = 16ft