Geometry

The answer is B. 19.

 

1. Recall the property of congruent line - segments:

In the given diagram, line - segments with the same number of tick marks are congruent. We can see that  and  both have one tick mark, so .

 

The property of congruent line - segments states that if two line - segments are congruent, then they have the same length. That is, if , then .

 

2. Substitute the given value of

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