This question has infinite answers, as the condition could be fulfilled by infinite combinations of A and B.
To illustrate,
If A = 20, B = 60, B-A = 40, the condition is met.
If A = 60, B = 20, A-B = 40, the condition is also met.
Enter the modulus sign (| |). We need |A-B| = 40
What does it do?
It makes whatever you put into it positive, showing you how ‘big’ the number is, regardless whether it is positive or not.
e.g. |-40| = 40, |40| = 40, |-1| = 1, |0| = 0
A and B can be interchanged, as the sequence of subtraction does not matter (only the difference does).
Plotting this graphically gives you the following. Any point on the plane has two values. The horizontal value is the A value. The vertical value is the B value.
Any point on the blue lines will meet the condition.
For instance, take the point where the top blue line crosses the vertical black line. At that point, horizontal value is A = 0, vertical value B =40.
The condition is met.
This condition would be fulfilled by infinite combinations, including A=1040 and B = 1080. It is not exhaustive.