And to check that, we multiply this out and we should get this form. And, in fact, we do. Now, our final step before we plug in chug is simply to rewrite this so that we have this thing on one side and everything else, all the knowns on the other side. So you want the unknown on one side and the knowns on the other side. And this is what we get. So what we do is we find the common denominator here, multiply this by Ti and this by TF, bring everything over, bring the R over, and then bring the negative over, and we get this.