In an arithmetic sequence, the 5th term is 18 and the 9th term is 30. What is the 1st term of the sequence?

✓ Correct Answer: Option B

Let the first term be 'a' and the common difference be 'd'. a + 4d = 18 and a + 8d = 30. Subtracting the first equation from the second gives 4d = 12, so d = 3. Substituting d=3 into a + 4d = 18 gives a + 4(3) = 18, so a + 12 = 18, and a = 6.