Explain why triangles in the figure are similar. then find the missing length x

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Step-by-step explanation:   6  26  18  13

The two outside angles are congruent.  The two inside angles are supplemental thus they are equal.  The last two angles the high one and the lower one must sum to 180° in their respective triangles so they are equal since their similar angles are equal.

find x

4 is to x as 5 is to 7.5

   4/x = 5/7.5      solve for x

   4 × 7.5 / 5  = x

    30 / 5  =  x

       6 = x

7 is the median   7.875 is the mean

step-by-step explanation:

3,4,5,6,8,11,13,13