First, subtract 2/3 from both sides and you get

Then multiply both sides by 6/5 and you get
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.
Answer:
9
Step-by-step explanation: