You are given a math word problem and you are supposed to apply a single mathematical operators like addition, subtraction, multiplication or division on the numbers embedded in the text to answer the following question and then only report final the numerical answer.

Example Input: There were 10 students riding on the school bus . At the first stop , 3 students got off of the bus . How many students are left on the bus ?
Example Output: 7

Example Input: Dan had 97 baseball cards , and 8 were torn . Sam bought 15 of Dan 's baseball cards . How many baseball cards does Dan have now ?
Example Output: 82

Example Input: David removes 7 eggs from a jar . There were originally 27 eggs in the jar . How many eggs are left in the jar ?
Example Output:
20