You can represent the two numbers with (n) and (n+18) bc one of the numbers is 18 bigger than another. Because they add up to 66, the equation would be n + n+18 = 66. By combining like terms, we can simplify that to 2n + 18 = 66. Then to get n by itself, subtract 18 from both sides to get 2n = 48, then divide both sides by 2 to get n= 24. That’s one of your numbers, and the other one is (n+18) which, since we know n=24, is 24+18, which = 42. So the two numbers are 24 and 42, and they add up to 66 so it works.