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

[EX Q]: Problem: how many prime numbers are between 51 / 13 and 89 / 9 ?
[EX A]: 2

[EX Q]: Problem: amit and ananthu can do a work in 10 days and 20 days respectively . amit started the work and left after 2 days . ananthu took over and completed the work . in how many days was the total work completed ?
[EX A]: 18 days

[EX Q]: Problem: a bottle contains a certain solution . in the bottled solution , the ratio of water to soap is 3 : 2 , and the ratio of soap to salt is two times this ratio . the solution is poured into an open container , and after some time , the ratio of water to soap in the open container is halved by water evaporation . at that time , what is the ratio of water to salt in the solution ?
[EX A]:
18 :