To solve this problem, we will setup a system.
We know that two numbers have a sum of 12 and a difference of 4.
So let's call our first number x and our second number y.
So we know that x + y = 12.
We can also say that x - y = 4.
Now rewrite the equations on top of each other.
x + y = 12
x - y = 4
Now we can use addition to solve this system.
When we add the equations together, the y's will cancel.
So we have 2x = 16.
Now divide both sides by 2 and x = 8.
Now plug an 8 back in for x in the first equation to find that y = 4.
So our numbers are 8 and 4.