Stack Exchange Data ExplorerMathematica, 66124 bytes
SELECT SCORE/CAST(ANSWERCOUNT AS DECIMAL)FROM POSTS WHERE ##N##=ID
N@("score"/.(u="items"/.Import["http://api.stackexchange.com/questions/"<>#<>"?site=codegolf","JSON"]))/("answer_count"/.u)&
Try it online! Mathematica has a data type called Rule
and it confuses the heck out of me. :P