Definition: 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: In Mr. Olsen's mathematics class, 0.7 the students received A's and 0.2 received B's. What fraction of the students received either A's orB's?

0.9