First, find the positions of C and D. Draw a diagram to visualize the problem:
To find c and d, divide the distance between A and B over 3. Then, add the result to the position of A to find c, and then add again that number to the position of c to find d.
The distance between A and B equals the difference of their coordinates:

Divide 27 over 3:

Add 9 plus 11 to find c:

Add 9 plus 20 to find d:

Since c=20 and d=29, then:

Therefore:
