Answer:
 9 cookies per dollar
Explanation:
This is a fraction equal to 
36 cookies ÷ 4 dollars 
 
We want a unit rate where 
1 is in the denominator, 
so we divide top and bottom by 4 
 
36 cookies ÷ 4 
--------------------------
4 dollars ÷ 4 
= 
9 cookies 
---------------
1 dollar 
= 
9 cookies 
-----------------
dollar 
= 9 cookies per dollar