What is the least common multiple of 3, 4a, 5b, and 6ab?

Me answer number 3plz explain how you do it

At the newest animated movie, for every 9 children, there are 4 adults. there are a total of 39 children and adults at the movie.

Jackie purchased 3 bottles of water and 2 cups of coffee for a family for $7.35. brian bought 4 bottles of water and 1 cup of coffee for his family for $7.15. how much does each bottle of water cost? how much does each cup of coffee cost? i need this done