Owl: You have 60 meters of flexible edging to border a rectangular herb garden against a long brick wall — the wall replaces one side, so edging covers only three sides. You want maximum planting area.
Optimization is a plot: translate the story into a function of one variable, find critical points where the derivative is zero or undefined, and check endpoints of the realistic domain.
A critical point is a candidate, not an automatic champion. Endpoints matter when the domain is closed.
If the side parallel to the wall is x and the perpendicular sides are each y, what's the constraint, and what's the area as a function of one variable?