Hello Aidan,
"The quotient of... and..." means that you are dividing the first "thing" by the second "thing." Here, you are dividing 4 by the difference between 7 and a number.
In other words: in the numerator you will have: 4
In the denominator you will have: the difference between 7 and a number: if x is that number, the difference is 7 - x
The final answer will be: 4/(7-x)
4
___
7-x