The roots are the x-intercepts, where the parabola crosses the x-axis. If the parabola opens up and it's vertex is below the x-axis then it crosses the x-axis in two places and has two (real) roots.
Step-by-step explanation: 80 divided by 5 is 16, so you would use 16 to find out how many students there are. To do that, you have to do 23 times 16, which is 368. Hope this helps!