Answer:
D) 5/12
Step-by-step explanation:
Suppose there are 30 girls at the school. Then the proportions tell you that 12 of them study music, and 5 of them study both music and dance.
Then 5 of the 12 girls who study music also study dance. That fraction is 5/12.
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We chose 30 because it is the least common multiple of the denominators of the fractions (2/5, 3/5, 1/6) in the problem statement.
Of course, you know that 2/5·30 = 12, and 1/6·30 = 5.
