instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: how many diagonals does a polygon with 13 sides have , if one of its vertices does not connect to any diagonal ?
answer:
54


question:
Problem: find the sum the difference between the compound and s . i . on a certain sum of money for 5 years at 20 % per annum is rs . 75 of money ?
answer:
1875


question:
Problem: if 75 percent of a class answered the first question on a certain test correctly , 70 percent answered the second question on the test correctly , and 20 percent answered neither of the questions correctly , what percent answered both correctly ?
answer:

65