Supplementary angles add up to 180°.
Assuming the angles are x and y, we have that

If one angle is 12° less than the other, we have the equation to represent the statement to be

We can solve both equations 1 and 2 simultaneously.
Let us substitute for y in equation 2 into equation 1:

To find y, we can put the value of x into equation 2:

Therefore, the values for each angle are 84° and 96°