The lowest possible score that Jake can have is 92.
To solve a problem like this, you need to find the average of the data set. To do that, you add up all the given numbers and divide the total by how many numbers were added up.
To find this answer, I just added in each letter one at a time (for C, I did 66+80+88+82+72+92, which equals 480, and then I divided it by 6 to get 80.) until I got an answer of 80.