ok to do this you have to start by guessing. its trial and error in this case. I would star with 30. 30 x 2 is 60. 60 x 2 is 120. 120 + 60 is 180. thats too much so lets lower our guess. 25. 25 x 2 is 50. 50 x 2 is 100. 100 + 50 is 150. so its dimensions are 25x50
