Problems Teaching

My First @solvemymaths Problem

This morning I woke up to the problem shown below by the excellent @solvemymaths on my Twitter feed.

I’ve always been very lazy and not properly solved any of his puzzles before, partly because I have a strange irrational fear of geometry. Wanting to conquer this fear I thought I’d have a quick go at this.
It turned out to be quite straight forward really (although I did make a silly mistake and got an original answer that seemed odd). My workings with my mistake are shown below: