From the Pythagorean theorem, we can relate the values:
We can rewrite the expression as it follows:
If we name this expression as: A: (x + 6) and B: (x - 8)
We now have:
The only way for this expression to be zero is if A of B, or both equal zero. From this, we have:
The first answer, x = - 6, has no real meaning because there no sense someone waked a negative amount of kilometers. From this, we know that Michelle walked 8 km.
The answer, as explained, is C: 8km.