Answer:
A. 8
Step-by-step explanation:
The length of the remaining side will be between the sum and difference of the given sides:
5 + 13 = 18 . . . . upper limit of 3rd side length
13 - 5 = 8 . . . . . lower limit of 3rd side length
The only answer choice in this range is 8.
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<em>Comment on question and answers</em>
Please note that this would not be an allowed answer for some triangle inequality questions. Some authors insist that the sum of the two shortest sides be <em>greater than</em> the longest side, so the triangle has non-zero area. Other authors allow the sum to be <em>greater than </em><u><em>or equal to</em></u> the longest side. The only viable answer choice here is one that makes use of the "or equal to" condition. The 5-8-13 triangle will look like a line segment of length 13. It will have no area.
