The length of a large rectangular room is 7 metres more than its width. If the perimeter is 34 metres, the length of the room, in metres, is:
Length = Width + 7
Perimeter = (Length) + Width + (Length) + Width = 34
(Width + 7) + Width + (Width + 7) + Width = 34
4·Width + 14 = 34
4·Width = 20
Width = 5
Length = Width + 7 ---> Length = 5 + 7 = 12