So what you would do is subtract 10 from 80 because you earn $80 and lose $10 out of that $80 every hour and you would end up with $70 and to find how long it would take to earn $700 is you would divide 700 by 70 and your final awnser would be 10 hours.
I didn't mean to post the answer and can't figure out how to take it down. Somebody report it so it does go down and the question can be later answered. Thank you