We want to solve the following equation

First, we start by distributing the multiplication on the left side, so we have

Note that if we compare this step to the second step of the given procedure, the mistake occured on the distribution of the multiplication. So, instead of writing -6, the mistake was to write -3.
Now, we continue to solve the equation from this point. First, we operate on the left side, so we get

Now, we subtract 1 from both sides

Then, we divide both sides by 2. So we get
