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: Tim found 679 seashells and 110 starfish on the beach. He gave 172of the seashells to Sara. How many seashells does Tim now have?

507.0