The correct answer is 720 I did this problem long time ago hope this helps :)
Solve for x:
x^9 = n x
Subtract n x from both sides:
x^9 - n x = 0
Factor x and constant terms from the left hand side:
-x (n - x^8) = 0
Multiply both sides by -1:
x (n - x^8) = 0
Split into two equations:
x = 0 or n - x^8 = 0
Subtract n from both sides:
x = 0 or -x^8 = -n
Multiply both sides by -1:
x = 0 or x^8 = n
Taking 8^th roots gives n^(1/8) times the 8^th roots of unity:
Answer: x = 0 or x = -n^(1/8) or x = -i n^(1/8) or x = i n^(1/8) or x = n^(1/8) or x = -(-1)^(1/4) n^(1/8) or x = (-1)^(1/4) n^(1/8) or x = -(-1)^(3/4) n^(1/8) or x = (-1)^(3/4) n^(1/8)
Half Tens is a way of multiplying where we have to find the value of given numbers. First we double any 'one' of the two given numbers and multiply both to get an answer. Then we divide that answer by '2' to get the answer.
Lets take two numbers as 16 and 340

Double the number 16

Now we will divide this by 2

So, if we check
, it is 5440.
Similarly if we double the number 340, we get 680
Now, 
And 10880/2 = 5440
Hence, in both ways the answer is 5440.
The correct answer is:
[B]: "

" .
__________________________________________________________Consider choice [A]: 
;
=

;
= 2 ; "2 ≠ -2" ; so we can rule out: "Choice [A]" .
__________________________________________________________Consider choice [B]: 
;
=

;
= "-2" ; Yes!
→ Let us proceed with the final answer choice ;
__________________________________________________________Consider choice [C]:

;
=

;
= 2 ; "2 ≠ -2" ; so we can rule out: "Choice [C]" .
__________________________________________________________The correct answer is:
[B]: "

" .
__________________________________________________________