a. 12 deg, b. 168 deg
We can create a systems of equations using this information, since supplement angles add up to 180 deg and complementary angles add up to 90 deg, when angle = x deg and supplement = y deg,
x + y = 180
y = 2(90 - x ) + 12
Solving:
x + 2(90 - x) + 12 = 180
-x + 180 + 12 = 180
x = 12
12 + y = 180
y = 168