Questions like this are "hard" in the sense that it can be easy to panic, or to lose focus, or to see the whole shape rather than how to break it up. Once you can see the four small triangles and the large square, it becomes perfectly manageable, but what makes it hard is being hit all at once with just one piece of info (a=1) and having to work out the rest. It's typical of an Edexcel-style question to do this, to test the problem-solving skills.
I don't think judging it outside an exam setting is quite fair. Agree that the solution in itself isn't A Level standard, but the ability to work through each step without "hand-holding" is.