Students were surveyed about their favorite colors one fourth of the students perfered red , one eighth of the students perferred blue, and three fifth of the remaining students perferred green . if 15 students perferred green , how many students were surveyed

Since 1/4 said red, and 1/8 said blue, that leaves 5/8 of the students remaining. 3/5 of those students said green, so we need to multiply 5/8 by 3/5, achieving a product of 3/8. If 3/8 of the students is 15 students, then we must divide 15 by 3 to get 1/8 of the students. 15 divided by 3 is 5, so if we multiply by 8, we get the total amount of students, being 40 students.