The given equation is not balanced. To balance it, we need to add coefficients to the reactants and products so that the number of atoms of each element is the same on both sides of the equation. Here's the balanced equation:

$$C + O_2 → CO_2$$

Now let's balance the equation step by step:

Step 1: Start with the carbon (C) atom. We have one carbon atom on the left side and one carbon atom on the right side, so this is already balanced.

Step 2: Move on to the oxygen (O) atoms. We have two oxygen atoms on the left side (in O2) and two oxygen atoms on the right side (in CO2), so this is also balanced.

Therefore, the equation is now balanced.