Let's start by writing the statement given, using mathematical terms:
The sum of two consecutive numbers: If one number is "x", the next one (consecutive one is "x+1". Then this statement can be written as:
x + (x+1)
Continue with the sentence:
Divided by their positive difference: The difference between two consecutive numbers must be "1" because they are built as the first one "x" and the following one: "x+1", then they must differ in one unit: "1"
continue with the sentence: ... is equal to 9
So now let's put all these together, and solve for the unknown "x":
[x + (x+1)] / [1} = 9
x + x + 1 = 9
2 x + 1 = 9
2 x = 9 - 1
2 x = 8
x = 8/2
x = 4