So, isomers are compounds that have the same molecular formula but different structures. So whenever we try to find isomers of alkanes, it usually helps to have a systematic approach, and that's exactly what we use in this example. Here, we have a set of four steps that we're going to follow to find our isomers. And, in fact, we can always use these same steps whenever we're trying to find isomers of alkanes. So let's begin with step one. Now, step one happens to be the easiest one, and you'll see why in just a second.