Standard practice
Area counts a region once, and a hole not at all.
A 12 by 8 rectangle has a 5 by 3 rectangle removed.
The area of a composite figure is the sum of parts that cover it exactly once. A hole or a cut-out is not added. A different cut of the same figure has the same area.
Problem 1 of 9. Activate, study a model, try guided items, work independently, apply, and reflect.