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

Ex Input:
Problem: robert ' s salary was decreased by 20 % and subsequently increased by 20 % . how much percentage does he lose ?

Ex Output:
4 %

Ex Input:
Problem: in the manufacture of a certain product , 8 percent of the units produced are defective and 5 percent of the defective units are shipped for sale . what percent of the units produced are defective units that are shipped for sale ?

Ex Output:
0.4 %

Ex Input:
Problem: the sub - duplicate ratio of 16 : 64 is

Ex Output:
2 :