I have a Masters (dunno if you consider that an indication of intelligence but it gives a reference point) and I am unable to do math.
The reason is that I sure can learn it, but I can only retain the information for a couple of days, a week at the most. Sure, the basics are no problem, but anything that's really abstract to me, I cannot retain it. I have the capacity to understand it, but I cannot fully grasp the meaning of it, because in the end...well it's just a bunch of meaningless numbers to me. It is hard to keep track of what represents what and that's when I start mixing formula's and start making gruesome mistakes.
I failed my finals for math and physics in high school, had to redo them. Now, I am fully aware that this was also because I refused to study the first semester, as to me, math and physics were torture. I didn't see the point of studying something I didn't find useful and couldn't retain anyways, and is boring to booth. However, since my finals were in danger in the second semester, I got tutored by my elder brother (industrial engineer), and he's a pretty good teacher actually. He explained me things that my teachers just skimmed over. We made a lot of progress. The next week he came back and wanted to continue and I told him: "Wait...start over. I don't remember squat." His jaw dropped on the floor and he couldn't believe it. But when he tested me, he noticed that although I still had some idea of the main baseline, the 'logic bridges' in between were missing, causing me to make very basic mistakes.
When I finally took the test, my teacher corrected it on the spot (oral exam), and shook his head. I'd flunked, at least on the practical part of the exam. He then tested my knowledge of formula's and the theoretical stuff without having to apply it, and I had it almost flawless (I have a photographic memory). My test on Statistics, which I studied at 5 am in the morning, turned out to be also flawless (again, we only had the basics so it wasn't hard and its less abstract). His jaw dropped to the floor as well. He'd assumed I was just lazy (which was correct), and that with proper studying I'd be fine (which was incorrect). His final words to me were: "You really just do not see it, do you?" I shook my head. I barely passed because of this, but it wasn't enough to make up for the first semester. In the summer, my brother worked with me intensively, and got me passing my tests. A week later, I had no clue anymore what I had answered or why on the tests. It is also the reason taht when I get a mathproblem, or a bunch of numbers, I freeze up. I *know* I will fumble up and get confused. And its a nightmare I personally don't feel like reliving. Oh and btw, it is possible to be haunted by numbers in your dreams!