18-21 year olds who voted were 85% of people 18-21 eligible to vote. In math, of means multiply.
85% * (people eligible to vote between 18-21).
8% of people eligible to vote are between 18-21, so that becomes .85 * .08 = .068 = 6.8 % of people eligible to vote who were 18-21 and who actually voted.
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