How do you find perimeter in general? You add up all the sides. So, let's do that. 2r+5+2r+4r-3+r= 6r+2. So, the perimeter is equal to 6r+2. But wait it is also equal to 38 (it is in the question). So, if both are the perimeter, they are the same. So, set them equal to each other.
