The answer is false, it is only true for postulates, not conjectures.
It's a vertical angle. Add the two angles 143+33=176
then divide by 2 , 176÷2=88
the answer is C. 88°
Here the given expression is

We need to find the value of y when x =3 . So we substitute the value of x in the given expression.

So when x=3, y=0.4 and that's the required answer.
This is a simple consequence of the Zero-sum problem: https://en.wikipedia.org/wiki/Zero-sum_problem