If you have a 55 going into and exam worth 20 percent and you get 50 percent what will your final mark be?

80 percent (4 parts out of 5) of your final grade consists of the 55. 20 percent (1 part out of 5) of your final grade consists of the 50. The final grade is (1/5 of) (55 + 55 + 55 + 55 + 50) = (1/5 of) (270) = 54 percent