The equation is simply 8s where s is the length of a side. There are 8 sides. You are just adding the length of all 8 sides together to get the perimeter.
I think 1 is the only common factor of both 0.20 and 215 but I'm not 100% certain
900 divided by 3 is 300 so 300 students bring their lunch opposed to 600 students who do not.
