If the sum of the first 15 terms of an arithmetic sequence is 135, and the first term is 3, what is the common difference?

What is the sum of the arithmetic sequence: 2, 5, 8, 11, ... up to the 15th term?

What is the sum of the first 5 positive even numbers in an arithmetic sequence?

What is the sum of the first 20 positive odd numbers in an arithmetic sequence?

If the first term of an arithmetic sequence is 6, and the sum of the first 12 terms is 216, what is the common difference?

What is the sum of the arithmetic sequence: 12, 16, 20, 24, ... up to the 7th term?

In an arithmetic sequence, if the sum of the first 10 terms is 85 and the common difference is –3, what is the first term?

In an arithmetic sequence, if the sum of the first 6 terms is 42 and the common difference is – 2, what is the 10th term?

If the first term of an arithmetic sequence is 3, the common difference is 4, and there are 8 terms, what is the sum of the sequence?

In an arithmetic sequence, if the first term is 15 and the common difference is 4, what is the sum of the first 12 terms?