To find the perimeter of a rectangle you have to add the four sides of the rectangle, you have two sides and know the perimeter, this will help you find the length of her room. 12 ft is the width, add 12+12 and you have 24. The perimeter is 50 so subtract 24 from 50 and you have 26 that is the length times two, so divide 26 by 2. Now you have 13, so the length of her room is 13 feet.
