Answer:
![\huge\boxed{ A\ union \ B = \{3,6,8,9,12\}}](https://img.qammunity.org/2021/formulas/mathematics/college/c7lpavqpup9xumu81oshmw4axmgcltii2e.png)
![\huge\boxed{A\ intersection \ B = \{6,9\}}](https://img.qammunity.org/2021/formulas/mathematics/college/ask0to026jgfigxn4odi2ym832ofhhqqx5.png)
Explanation:
A = {3,6,9,12}
B = {6,8,9}
A∪B = {3,6,9,12} ∪ { 6,8,9} [Union means all of the elements should be included in the set of A∪B]
=> A∪B = {3,6,8,9,12}
Now,
A∩B = {3,6,9,12} ∩ {6,8,9} [Intersection means common elements of the set]
=> A∩B = {6,9}