I need answers ASAP! No links please! Please explain/show work! Thank you!
Bobby had a party while his parents were away for the weekend. Bobby estimated that if his 9 friends help him to clean the house, they will be able to finish cleaning in 8 hours before his parents return. After two hours of cleaning, Bobby's parents call and say they are just two hours from home. How many more friends does Bobby need to call for help to finish cleaning in time?