Answer:
C. 6.9
Explanation:
Pretend this is a 2-d diagram and use the Pythagorean theorem.
Pythagorean theorem: a^2 + b^2 = c^2
a = 6 mm
b = 7/2 = 3.5 mm
c = x
6^2 + 3.5^2 = x^2
36 + 12.25 = x^2
48.25 = x^2
x = 6.9
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