My, age 17, did it in 10 seconds.
My father, age 45, did it in 20 seconds (and he is also good at maths).
People thought it was very hard because of the larger hold of social media. People who found it hard (who are not good at maths), all went straight to twitter after the exam to complain about it.
I have spoken to my previous maths teacher, as he teaches GCSE [I am studying A-Level maths now]. He said, all the good maths students found it easy. They did not complain. All the bad students gave it a try, but could not see the step of making it into the equation "6/n*5/(n-1)=1/3", so they struggled.
It is not a problem with our education, only a problem with people emphasising something on social media.