haha yeh my brain skimmed over it...
in line c, she minused 2 from the left hand side, rather than adding that!
I reckon it was tricky! My brain just saw the difference of 2, and read over it! sooo easy
This took me a few readings to see as well, but i found it. I thought it might have been down the bottom in the dividing and focussed on that for a bit. then I saw it, like hidden there.