Wait on the car and taks the calculus again. I had to take calculus several times before I got it myself. I needed it for my mechanical engineering classes and for business classes. I never used calculus again after school but you have to prove you can learn it to get the degrees. All the rest of the courses were pretty easy for me but that calculus was a real struggle. I have felt your pain.
A car will be there for you later, get the education you desire now. It will be much more challenging to get the education later in your life, TRUST ME on this one.
It is also much easier to make excuses for what you drive now while you are still in school than it is to make excuses for the rest of your life for not getting that degree you always wanted.
-Mark.