So here's my question: (by the way, please don't penalise me for putting it in the wrong forum - i didn't see one for graphs!)

The cross section of a hayshed is in the shape of an inverted parabola. It can be

modelled by the equation:

h = 0.3w(8 - w)

where w is the width of the hayshed, and h is the height. Solve w (width).

Please explain how you worked it out?