text: The area is 100 _m_? I don't think so - area is measured in square meters.\n\nAssuming that that's just a typo, the proper setup is 100=(w+2)(w+10)-w(w+8) -- the area of the pool+walkway minus the area of the pool. Simplifying:\n\nw²+12w+20-w²-8w=100\n4w=80\nw=20\nL=28\n\nedit: corrected typo