In substituted alkanes, the substituent is given a number based on the position on that carbon backbone, and the number value should be as low as possible. So let's go to example number one. So, our substituent is this methyl group. Now, if we start from this side, we go one, two, three. So, our methyl is on the third position of the carbon backbone. If we start from this side, it's also on the third.