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

Example Input: Problem: of 30 applicants for a job , 9 had at least 4 years ' experience , 18 had degrees , and 3 had less than 4 years ' experience and did not have a degree . how many of the applicants had at least 4 years ' experience and a degree ?
Example Output: 10

Example Input: Problem: if a = 105 and a ^ 3 = 21 × 25 × 45 × z , what is the value of z ?
Example Output: 49

Example Input: Problem: a man can row a distance of 5 km in 60 min with the help of the tide . the direction of the tide reverses with the same speed . now he travels a further 20 km in 10 hours . how much time he would have saved if the direction of tide has not changed ?
Example Output:
6