Instructions: You are provided with an arithmetic question. Your task is to compute the solution using the given arithmetic operations. The only arithmetic operators needed to answer the questions are'+'(addition) and'-'(subtraction). The answer should be correct to one decimal place.
Input: Melanie had 30 baseball cards, and 9 were torn. Sara bought 18 ofMelanie's baseball cards. How many baseball cards does Melaniehave now?
Output:
12.0