Excellent question.
First since Cot is the opposite of Tan we must first find Tan.
The formula for Tan is Opposite/Adjacent, in this case that would be 9/12.
Now to get Cot we must flip 9/12 to get 12/9.
Finally we simplify by dividing the top and bottom by 3 to get 4/3.
The answer here is 4/3!
Hope this helps (: