soln from P.C.S. CREATION in comments
(21+6) – (21/3)= 27-7= 20
(36+8)-(36/3)= 44-12=32
(9+12)-(9/3)= 21-3=18
(4+3) – ( 3/3 )= 7 – 1 =6

it follows this pattern
axa = (a-1) + (a-1)

thus 6×6 = 5 + 5 = 10

Answer is 71

as numbers add upto a multiple of 10 in every atom.

ex. 0 + 3 + 14 + 2 +1 =20
2 + 10 + 24 + 6 + 8 = 50
only option which can make the sum to a multiple of 10 for 4 + 14 + 5 + 6 is 71.

answered by Ram Balaji in disqus comments

Its actually pretty simple

all the rows sum is 15

first row => 9 + 1 + 5 => 15
second row => 4 + 8 + 3 => 15
third row => 2 + ? + 7 => 15 => ? = 15 – 7 -2 => 6