<p>Forget about the exterior space and focus only on the 40 x 130 rectangle which the 30 x 30 shelter must fit in. First look at how many times you can put the edge (30 ft) on the 130 ft border. You can see that this is 11 (from the shelter’s edge starting all the wat in the corner to thirty feet from the far edge). Doing the same with the 40 ft border, its obvious that there are only two ways to postion the shelter (along each opposite edge). We therefore have 2 sets of 11 possibilities, or 2 * 11 = 22 total locations.</p>
<p>I know this may be very difficult to visualize or follow, but using the picture can really help.</p>