From trigonometry we know that:
if 
then,
(where
is an integer)
This can be rewritten in degrees as:
.............(Equation 1)
Now, in our case, 
Therefore, (Equation 1) can be written as:
..........(Equation 2)
Now, to find the correct options all that we have to do is replace n by relevant integers and find the values of
that match.
For n=2, (Equation 2) gives us:
.
Thus, 
Now, we know that: 
Let n=-1, then:

Thus, 
Likewise, 
Only the last option
will never match
because no integral value of
will ever give 
Thus the last option is the correct option.
Answer:
Actually,there x is qual to ninty minus x because of vertically opposite side...cauce ninty minus x comes in vertical opposite side by dragging the ninty minus x down ...so finally x is equalto ninty minus x and two x is equal to nintynow divide ninty by nine it's your ans.