In total he ran 19 miles based off of how the question looks. It looks like I needed to add each number up.
Answer:
One of it culd be -3 or 3
Step-by-step explanation:
It's dependent on the context. A book may ask you to find the f'(x) of a function and you may have to use a u sub in your problem which requires you to find the dy/dx of what you substitute. So in this case both would be used.
