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

Ex Input:
Problem: a train 300 m long is running with a speed of 68 kmph . in what time will it pass a man who is running at 8 kmph in the same direction in which the train is going ?

Ex Output:
18 sec .


Ex Input:
Problem: a student chose a number , multiplied it by 2 , then subtracted 138 from the result and got 102 . what was the number he chose ?

Ex Output:
120


Ex Input:
Problem: an alloy of copper and zinc contains copper and zinc in the ratio 8 : 2 . another alloy of copper and zinc contains copper and zinc in the ratio 4 : 6 . in what ratio should the two alloys be mixed so that the resultant alloy contains equal proportions of copper and zinc ?

Ex Output:

3 : 1