10 people because all the sisters have the same brother so 7+1+2.
All of these sets meet the requirements of the triangle inequality. The sum of any two numbers in the set is greater than the third one. (You really only need to check that the sum of the smallest two is greater than the largest.)
It can help to resolve the numbers that are only indicated as to value.
√13 ≈ 3.606
2√10 ≈ 6.325
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Your comparisons can be ...
2 + 3 = 5 > 3.606 . . . is a triangle
5 + 5 = 10 > 6.325 . . . . . . is a triangle
5 + 12 = 17 > 15 . . . . . . . . is a triangle
<h3>
Answer: Choice C</h3>
The base 16 is the same as 4*4.
From there, the rule 
is used to get 
Afterward, the exponents are added getting 1/2+1/2 = 2/2 = 1. The rule is 
which only works if the bases are both the same.
