Which of the following numbers will replace the question mark (?) in the given series?

Given series:

168, 191, 218, 249, 284, ?

Step 1: Find differences

191 − 168 = 23

218 − 191 = 27

249 − 218 = 31

284 − 249 = 35

So the pattern of differences is:
23, 27, 31, 35

This is increasing by +4 each time.

Step 2: Find next difference

Next difference = 35 + 4 = 39

Step 3: Add to last term

284 + 39 = 323

Final Answer:

323