The ratio of the number of adults to the number of children in an event hall was 5:7.
(a)After 60 adults and 84 children entered the event hall and no one left the event hall, what was the ratio of the number of adults to the number of children in the event hall?
(b)A while later ,56 adults and 56 children left the hall and the ratio of the number of adults to the number of children became 7:13.
How many children were there in the event hall at first?