BBs, if you find this hard it's most likely because you have a mental block on math. Think of Math in a more interesting way just as measuring and sizing tool in 3d programs are, but in real life.
Here is a hint: A straight angle Is always half of 360 degrees, as if it cut a circle in half; meaning it's 180 degrees.
Now, if x is given for one angle of a line then you simply minus that number from 180 and you'll get the opposite angle.
After you learn the procedure it becomes relatively easy.
Now when you get into higher math like Algebra 2 you'll be solving long division and beyond. For this stuff you'll need to concentrate.