Question 676561
First, let's find A and B. It is obvious, once you understand the problem, that A is 57 and B is 21. 
57 and 21 meet the criteria: 57+21=78  57-21=36 
Now that we've figured out the numbers, it is time to divide them: 57/21 
That reduces to 19/7. 
So, your answer is 19/7, or 2.714... 

Here's how I found out the answer: 
First, let's find the difference. 78-36 is 42. Half of 42 is 21. Thus, the smaller number is 21. Then, it's substitution from there.