It isn't simple if you have cognitive decline which is EXACTLY why Biden hasn't taken one or hasn't revealed that he scored poorly on the exam. Biden could put to rest the whole dementia issue if he would have a third party give him a standard Montreal Cognitive Assessment exam and make the results public. But he won't do it because he would score poorly. My guess below a 26.
Your guesses may fit you, but not Biden. Of course, you have not listened to him speak, with an adult vocabulary and in complete sentences. I bet you miss the good old days of Trump when he insulted anyone who asked him a question that was not a setup. Then he would say they are working for a failing newspaper or TV station. I bet you miss a prez doing that. Trump is not bright. He talks like a teenager. A teenage bully.