Answer:
Work shown below!
Step-by-step explanation:
Number 12a:
[tex]a_{n}=a_{1}+d(n-l)\\ a_{n}=18+5(n-1)\\a_{12}=18+5(12-1)\\a_{12}=18+5(11)\\a_{12}=18+55=73\\[/tex]
Number 12b:
[tex]a_{n}=a_{1}+d(n-1)\\a_{n}=-8-6(n-1)\\a_{12}=-8-6(12-1)\\a_{12}=-8-6(11)\\a_{12}=-8-66\\a_{12}=-74\\[/tex]
