The answer sheet also tells what percentage of people gave each answer. So you will see that many of the questions you missed were hard questions for people in the class generally.
To adjust for differences in the difficulty of tests from one year to the next, I grade on the curve. So to judge how you did, you need to compare your score to how other students did. Multiply the number you got right by 3.3% to get your score to compare to the overall distribution of scores.