A so-called ‘child-friendly’ brainteaser has left Brits scratching their heads. But it turns out, there’s a rather simple but cheeky way to solve it that requires you to really think outside the boxA so-called ‘child-friendly’ brainteaser has left Brits scratching their heads. But it turns out, there’s a rather simple but cheeky way to solve it that requires you to really think outside the box