Solution:The pattern followed here is :(First number)²+(Second number)²⇒ Total/2 = (First row number)
(4)² + (6)² ⇒16 + 36 = 52,    52/ 2 = 26
(7)² + (1)² = 49 + 1 = 50;  50 / 2 = 25
Similarly,
(5)² + (3)² = 25 + 9 = 34;
34/2 = 17
Hence, "17" is the correct answer.