1) Let's gather all the data
Width: 20'
Length: 2w-5
2) Now we can plug that into the formula for the are of a rectangle, like this
[tex]\begin{gathered} A=wl \\ A=20\cdot(2(20)-5) \\ A=20\cdot(40-5) \\ A=20\cdot35 \\ A=700ft^2 \end{gathered}[/tex]Notice that we have plugged into that the width w=20. Therefore the area of the living room is 700ft²