Answer:
4 and 16
Step-by-step explanation:
First, let's find first term using sum formula:
![\displaystyle \large{S_n = \frac{1}{2} n[2a_1 + (n - 1)d]}](https://tex.z-dn.net/?f=%20%5Cdisplaystyle%20%5Clarge%7BS_n%20%3D%20%20%5Cfrac%7B1%7D%7B2%7D%20n%5B2a_1%20%2B%20%28n%20-%201%29d%5D%7D)
We know that d or common difference is 12 and only sum of two terms so n = 2.
![\displaystyle \large{S_2 = \frac{1}{2} (2)[2a_1 + (2- 1)d]} \\ \displaystyle \large{S_2 = 2a_1 +d}](https://tex.z-dn.net/?f=%20%5Cdisplaystyle%20%5Clarge%7BS_2%20%3D%20%20%5Cfrac%7B1%7D%7B2%7D%20%282%29%5B2a_1%20%2B%20%282-%201%29d%5D%7D%20%5C%5C%20%20%5Cdisplaystyle%20%5Clarge%7BS_2%20%3D%20%202a_1%20%2Bd%7D)
Since sum of two numbers equal 20.
![\displaystyle \large{20 - 12= 2a_1 +12 - 12} \\ \displaystyle \large{8= 2a_1 }](https://tex.z-dn.net/?f=%20%20%5Cdisplaystyle%20%5Clarge%7B20%20%20-%2012%3D%20%202a_1%20%2B12%20-%2012%7D%20%5C%5C%20%20%20%5Cdisplaystyle%20%5Clarge%7B8%3D%20%202a_1%20%7D)
From above, subtract both sides by 12, solving for a1.
![\displaystyle \large{8= 2a_1 } \\ \displaystyle \large{4= a_1 }](https://tex.z-dn.net/?f=%20%20%5Cdisplaystyle%20%5Clarge%7B8%3D%20%202a_1%20%7D%20%5C%5C%20%20%5Cdisplaystyle%20%5Clarge%7B4%3D%20%20a_1%20%7D%20)
Therefore our first number is 4.
Finding next number, create an equation:-
![\displaystyle \large{4 + a_2 = 20 } \\ \displaystyle \large{4 - 4 + a_2 = 20 - 4} \\ \displaystyle \large{ a_2 = 16 }](https://tex.z-dn.net/?f=%20%5Cdisplaystyle%20%5Clarge%7B4%20%2B%20a_2%20%3D%2020%20%7D%20%20%5C%5C%20%20%5Cdisplaystyle%20%5Clarge%7B4%20%20-%204%20%2B%20a_2%20%3D%2020%20%20-%204%7D%20%20%5C%5C%20%5Cdisplaystyle%20%5Clarge%7B%20a_2%20%3D%2016%20%7D%20%20)
Another number is 16
So 4 and 16 has 12 as difference because 4+12=16 and 16-12 = 4