A1=12, a2=27, a3=42, etc. The pattern is that you’re always adding 15 after starting with 12. So the general rule is...
an=12+15(n-1)
So then...
a18=12+15(18-1)
a18=12+15(17)
a18=267
Combine 3, 5, 9. then combine 4, 2, and 2.
Answer:
336
Step-by-step explanation:
hope this helps!
