Observe rows and columns

The best fit based on a logical guess is to take the middle number as the average of the first and third number in each row:

middle
=
first
+
third
2
middle=
2
first+third
​

For the missing number in the third row:

64
=
93
+
?
2

⟹

2
×
64
=
93
+
?

⟹

128
=
93
+
?

⟹

?
=
35
64=
2
93+?
​

⟹2×64=93+?⟹128=93+?⟹?=35
Final answer:

The missing number is 35.