If a₂ = 12 and d = 9, what is the 7th term?

Correct answer: 57

The governing concept is finding a term of an arithmetic progression from another known term. Instead of restarting from the first term, use aₙ = aᵣ + (n − r)d. Here the known term is a₂ = 12, the required term is a₇, and d = 9. The number of equal steps from the second position to the seventh position is 7 − 2 = 5, not 7. Therefore a₇ = 12 + (7 − 2)×9 = 12 + 5×9 = 12 + 45 = 57. Hence option B is correct. The distractors can result from adding the common difference the wrong number of times or from a simple arithmetic error. Counting gaps between positions prevents that mistake.