The longterm effects of chronic marijuana abuse, obviously. Math is hard:
“Well, the math stuff I was fine with up until about seventh grade,” Obama said. “But Malia is now a freshman in High School and I’m pretty lost.”
Really good job of vetting this clown, mainstream media.

But the media DID vet this clown. If by vetting, you mean tongue bathing.
Math? WTF – He struggles with original thought!
It’s a damn good thing he’s got Tim Geither to do the accounting and handle the math. Without Turbo-Tax Tim where would we all be? Woe is me.
Look at it from Obama’s point of view. Were Karl Marx, Vladimir Lenin, or Che Guevara known for their math skills? Hell no. Besides math is usually racist especially when it comes to financial matters.
I don’t know whether there is a serious element that underlies his obvious joke, but it’s very possible that Obama has very high level verbal skills but has more or less average math and spatial reasoning skills.