To find this out, you just need to multiply 1/8 by 24 (in mathematics, 'of' always implies multiplication).
To make it easier, we can make 24 into a fraction by putting a 1 under it to make it 24/1. All real numbers can be converted into fractions this way.
Then we multiply.
When multiplying fractions, you just need to multiply the numerators together, and then the denominators together, so the problem would go something like this:
1/8 * 24/1
is the same as
(1 * 24) / (8 * 1)
Since 1 times anything is the number that the one multiplies, the fraction reduces to 24/8, which can be simplified to 3.
1/8 of 24 students is 3 students.
Hope that helped =)
