Answer:
A. (4, 18)
Explanation:
The "y" coordinate of the midpoint will be equal to the average of the y coordinates of the endpoints, and the x coordinate of the midpoint will be equal to the average of the x coordinates of the endpoints, and so we get that...
The x coordinate of the midpoint = (5 + 3) / 2 = 8 / 2 = 4
The y coordinate of the midpoint = (21 + 15) / 2 = 36 / 2 = 18
So the right answer is A (4, 18)