1/3 of the students walks
1 -1/3 = 2/3 so 2/3 of the students do not walk
of the student who do not walk 4/5 take the bus
2/3 * 4/5 = 8/15
8/15 of her students take the bus
There must be at least 15 student
We only want whole numbers of students, so they must be in multiples of 15
15,30,45,60 etc
Mrs H has either 15 or 30 students. Higher multiples would be too many students in the class