Algebra-1

Question Analysis
This question tests the student's ability to use the explicit formula for an arithmetic sequence to find a specific term when given two other terms in the sequence.

Key Concept Explanation
The explicit formula for an arithmetic sequence is , where is the -th term, is the first term, is the common difference, and is the term number.

Step-by-step Solution
1. Identify the given terms: and .
2. Use the explicit formula to set up equations for the 4th and 8th terms:
For the 4th term:
For the 8th term:
3. Subtract the first equation from the second to solve for