Correct Answer: 25

Solution : Given:

The pattern can be observed running vertically down the columns.
Column 1: (17 × 21) + (17 + 21) + 1 = 357 + 38 + 1 = 396
Column 2: (18 × 22) + (18 + 22) + 1 = 396 + 40 + 1 = 437
Column 3: (19 × (?)) + (19 + (?)) + 1 = 520
⇒ (19 × (?)) + 19 + (?) = 520 – 1
⇒ (19 × (?)) + 19 + (?) = 519
⇒ (19 × (?)) + (?) = 519 – 19 = 500
⇒ (?) × (19 + 1) = 500
⇒ (?) × 20 = 500
⇒ (?) = 500 ÷ 20 = 25

So, 25 is the missing number. Hence, the third option is correct.