"If goods were sold only for cash, prices would be lower and everyone would be better off." no because some people wouldn't be able to live and i don't know y prices would be lower  

"If I can't pay for something, it means I can't afford it, so I won't buy it."  Yes because this is a good way to avoid debt and only get what you need.

"I buy on credit whenever I can because credit increases sales and is good for businesses." No because people get into debt because they dont have the money to pay for it and never do 

"You should use credit sometimes: it helps you establish a credit rating, which may be useful in case of an emergency." yes because they are right you do need a good credit rating