Hi there!
The answer is 0.
Since the question states that a and b are the same distance from zero, it must also mean that -a = b.
First, let's work with an example.
Let's say b is -4 and a is 4.
-4 + 4 = 0
We can do another example:
a = 7
b = -7
-7 + 7 = 0
This works with any number, so the answer is zero.
Hope this helps!