The task is to generate the correct answer for a given math problem.

Example Input: Problem: a question paper has 2 parts , a & b , each containing 8 questions . if a student has to choose 8 from part a & 4 from part b , in how many ways can he choose the questions ?
Example Output: 70

Example Input: Problem: the sum of ages of 5 children born at the intervals of 3 years each is 55 years . what is the age of the youngest child ?
Example Output: 5 years

Example Input: Problem: how many liters of water must be added to 18 liters of milk and water containing 10 % water to make it 70 % water ?
Example Output:
36