Explanation:

The number is 7 6 5 2 3 4 8, 

after subtracting 2 from odd digit and add 1 in even digit the new number is get 

= 7(-2)  6(+1) 5(-2) 2(+1) 3(-2) 4(+1) 8(+1) = 5733159

In 5733159 second digit from the right is 5 and third digit from left is 3,

By adding 3+8 = 8.

Hence, option 2 is the correct answer.