I never fully got math. Something about having some really stuffty physics teachers (both in high school and in university the last few years) made me brain dead when it comes to complex math stuff, like trucks with ramps on them with weight boxes attached to the top of the ramp accelerating at whatever and then asking you to measure the tension / angle of the rope.
Calculus though, that I can wrap my head around fairly easy, although I've already forgotten most of it thanks to that god awful linear algebra course I was forced to take.