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What is 2 8/10 + (-3.5) in decimal form

Plz heeeeeeelp plz give me the answer

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.)

Type the correct answer in each box, round your answers to the nearest integer 20 25 30 in the figure, the perimeter of hexagon abcdef is approximately w units, and its area is square units