If aₙ = 9n − 4, what is a₈ − a₃?

Correct answer: 45

The governing concept is substitution into an explicit sequence rule, followed by subtraction of two terms. For the eighth term, substitute n = 8: a₈ = 9(8) − 4 = 72 − 4 = 68. For the third term, substitute n = 3: a₃ = 9(3) − 4 = 27 − 4 = 23. Therefore a₈ − a₃ = 68 − 23 = 45, so option B is correct. A useful shortcut is that the constant term cancels: (9 × 8 − 4) − (9 × 3 − 4) = 9(8 − 3) = 45. Option A could result from an arithmetic error, while options C and D do not follow from the required evaluations. Both terms must be calculated using their correct indices before finding the difference.