Whats the price that generates the most profit with the function of -80p²+2720p-19,200?

$17

You're looking for the vertex, which is the highest point of the graph.
The graph is in the form ax^2 + bx + c, where a, b, and c are constants. The x-coordinate can be found by using -b/2a, which in this case would be -2720/(-160) which equals 17 since the negatives cancel out. This is the price for each individual product that you would make a maximum profit from