Which of the following numbers will replace the question mark (?) in the given series?
287, 195, 286, 189, 284, 184, 281, 180, ?

This is an alternating series consisting of two separate sub-series:
Sub-series 1 (odd positions): 287, 286, 284, 281, ?

287−1=286

286−2=284

284−3=281

Following the pattern, the next term should be 281−4=277.

Sub-series 2 (even positions): 195, 189, 184, 180

195−6=189

189−5=184

184−4=180

The question mark (?) falls at the 9th position, which belongs to Sub-series 1.
Therefore, the next number is 281−4=277.