Answer C.
Statement 1: we know only the ratio between women, children and men => dont know anything about the total number of people or the number of women/ children => can't calculate the number of men => insufficient.
Statement 2: No info about men or relationship between men and children => insufficient.
Combine (1) & (2): we have:
Women : Children = 7 : 2. => we can express the number of women and children as 7x and 2x respectively.
Children : Men = 3 : 5 => the number of men = the number of children : (3/5) = 2x : 3/5 = 10x/3 => x must be the multiplier of 3
Since, the number of children in the group is between 10 and 15 => 10 <= 2x <= 15. Thus 5<=x<=7 => x = 6 => Number of men = 20
Hence, the answer is C.
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