When a question asks you to make something the subject of an equation, it is asking you to rearrange it to get it in the form of, for example when 'p' is the subject, 'p = ....'

First we want to expand the brackets, 

4p - 8q = 3p + 2

Then we want to get rid of the '-8q' on the left side, we do this by adding 8q to both sides (-8q + 8q = 0, that's why it 'disappears' from the left side)

4p = 3p + 2 + 8q

Now, notice how we have 'p's on both sides? We want to get them together onto one side (because the question was to make 'p' the subject), so we minus 3p from both sides (remember, you have to do the same thing to each side!)

p = 8q + 2