The easiest way to approach this problem is to use algebra. We can define the two numbers based on “x”. We know that one number is just a number, but the other is that number plus four. In this case, we can say that:
(x) + (x+4) = 18
2x + 4 = 18
2x = 14
x = 7
We now know that one of the numbers is 7; if we plug 7 in place of “x” in (x+4), we learn that the other number is 11. You can check this by verifying that 11 is four more than 7 (it is!) and that 11 + 7 equals 18 (it does!).
Hope this helps!