First off, if it's mixed, you'd want to convert it to "improper" first, and then do the division... say hmm - 3 and 1/7

the line over the decimal part is because is a "recurrent decimal", or repeating one.
30b+3= s
It would be thirty students times the number of buses, with an addition of 3 students equal to the total number of students when on the field trip.
I hope this helps!
~cupcake
The story is telling who goes to the beach and at what time