I am really confused with this math question, please help!?

For a quadratic function, it has to be in the general form y = ax^2 + bx + c. You can "construct" this hypothetical arch on a set of x-y axes as follows: it has to be 15m high, so one point on your parabola is (0, 15); it has to be 6m wide at a height of 8m, so that gives you two more points: (-3, 8) and (-3, 8). With these three points, which are all (x, y) pairs, you can substitute them into the general equation above and it will give you a system of three equations, with three variables, and that can be solved algebraically.