Help me pls. What is the lenght of BC?

Turner's mom measured his room to see how long the wallpaper border needed to be. if two walls are 15 feet long and two walls are 12 feet long, how long should the strip of border be cut?

2y= 3 2 x−2 y = − 1 3 x + 1 y=− 3 1 x+1

If the ratio of sum of the first m and n terms of an ap is m2 : n2 , show that the ratio of its mth and nth terms is (2m − 1) : (2n − 1).