Idon't understand this. my teacher wasn't at school and this was homework

Use the frequency distribution, which shows the number of american voters (in millions) according to age, to find the probability that a voter chosen at random is in the 18 to 20 years old age range. ages frequency 18 to 20 5.9 21 to 24 7.7 25 to 34 20.4 35 to 44 25.1 45 to 64 54.4 65 and over 27.7 the probability that a voter chosen at random is in the 18 to 20 years old age range is nothing. (round to three decimal places as needed.)

(-y to the power of 2 - 4y- to the power of 2 -6 y +3)

Factor 15x^3 - 5x^2 +6x-2 by grouping. what is the resulting expression