Oh how I feel your pain on this math issue!!! When I was doing my undergrad, I wanted to jump in front of a moving car, because of the math class I was required to take. Don't get stressed, you can do this!!!
NOOOOOOOOOO put down the cold stone its alright yo math has not been your strong point but you are trying dont give up the class isnt over yet
First thing, talk to the teacher, have her tell you what your weak points are.The other thing is people say math is memorizing the formula. That was why I failed it so much because I wasn't memorizing the formulas. or like you I wasn't remembering to add the symbols and measurements. Math is not the strong point of most artists.Don't let it eat you up inside.Seriously though have a sit down with the teacher bring your test papers and ask her for help. If she/he/it won't help you find a math teacher that will. Like just really sit down and talk it out with them about the trouble your having. Maybe you can figure it out with their help.