Let's call the first number n, and the second number m.
n = 2m + 9 (9 more than twice the second number)
If the sum is 129, that means n + m = 129.
Now we can substitute the first expression (n = 2m + 9) into the second expression (n + m = 129), replacing the n.
(2m + 9) + m = 129
3m + 9 = 129
3m = 129 - 9
3m = 120
m = 120/3
m = 40
Now that we know m, we can find out n by replacing the m with 40 in the first expression (n = 2m + 9):
n = 2(40) + 9
n = 80 + 9
n = 89.
Therefore, n = 89, and m = 40.
