The opposite of 8 is taken, and then the opposite of that result is taken. Which value does the second step give?

Explication

Each step replaces a value by the one that adds to zero with it, so 8 gives -8 and -8 gives 8 back again. Stopping at -8 counts a single reversal and treats the second instruction as a repeat of the first, while -16 doubles the size, which reversing a sign never does.