One number is 9 more than twice another number. if the sum of the number is 129, find both numbers.

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.

a.) is the correct answer.

explanation:

conservation of mass

mass before something happens = mass afterwards