Question

If the difference of two consecutive numbers is 15 and the greater of them is x, then the smaller number is ?

Answer 1

geez - pick a couple of numbers and see what you get.
"difference" means subtract. So, the smaller is
x-15
The only problem I see here is that consecutive numbers are usually like 3,4,5,6,7,...
so I can't see how two consecutive numbers can differ by 15.

Answer 2

Do you mean the Sum = 15? If so:
X = The larger #.
x-1 = Smaller #.

x + (x-1) = 15.
X = 8.
X-1 = 8 - 1 = 7.