Answer:
12/13
Step-by-step explanation:
The cosine of an angle in a triangle can be calculated as a relation between the adjacent side and the hypothenuse. So, in this case the adjacent side of θ is 24 and the hypothenuse is 26.
Then:
cos(θ) = 24/26 = 12/13
The 'x' coordinate of the midpoint is the average of the 'x'
For this case we must indicate an expression equivalent to:

For properties of powers we have to:

So, the above expression can be rewritten as:

Thus, the resulting expression is: 
Answer:

Option D