If you work by process of elimination all you have to do is take 27 away from the bigger degree of the two and see if it is 2x as much as the smaller degree.
Students with D's / total students : 3 / (7 + 9 + 11 + 3 + 2) = 3 / 32 = 0.0937...to turn to a percent, multiply by 100 = 9.375....rounded = 9.4% <== ur probability
