Lets break it down:
I think “nine minus” is clear — it starts off with “9 - something”.
Now, a quotient is the result of division. For example, the quotient of 10/5 is 2, or the quotient of 16/2 is 8. Since in the phrase “quotient of two and x” two comes first, we are diving 2 by x. This is the quotient (2/x).
So to add it all together:
9 - 2/x would be your expression.