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

Ex Input:
Problem: gopi gives rs . 90 plus one turban as salary to his servant for one year . the servant leaves after 9 months and receives rs . 60 and the turban . find the price of the turban .

Ex Output:
30


Ex Input:
Problem: the ratio between b and y is 7 / 9 ; b and y are increased by 4 , what is the ratio between the new values of b and y ?

Ex Output:
it can not be determine


Ex Input:
Problem: in one alloy there is 10 % chromium while in another alloy it is 6 % . 15 kg of the first alloy was melted together with 35 kg of the second one to form a third alloy . find the percentage of chromium in the new alloy .

Ex Output:

7.2 %