Students were surveyed about their favorite colors one fourth of the students preferred red 1/8 of the students preferred blue, and3/5 of the remaining students preferred green. if 15 students prefer green how many students were surveyed

25 students were surveyed in total.

make all the fraction have the same denominator and you will get 3/5=24/40
1/4=10/40 and 1/8=5/40. 

24/40 is equal to 60%

therefore 15 kids like the color green which is the same thing to 60% of the kids asked like green. 15 is 60% of 25, therefore 25 kids were serveyed

I  dont  know much about vertexes but i know to solve this function you need to use foil method and then corresponmd the vertex with the actual coordinates, hope i !