On a multiple-choice test over English vocabulary, Roy got 16 out of 20 correct. What percent of the problems did she miss? Round your answer to the nearest tenth of a percent, if necessary.

How many liters of peroxide should be added to 12 liters of an 8% peroxide solution so that the resulting solution contains 16% peroxide?   original added new amount of peroxide 0.96 liters x 0.96 + x amount of solution 12 liters x 12 + x 0.18 liter 1.14 liters 1.92 liters 2.10 liters