This question is about triangles with their bases
on the same line and a shared side, like the ones
below:

The numbers in the triangles represent their areas.

The diagrams are not drawn to scale - can you create diagrams with
the correct areas drawn to scale?

Convince yourself that there are many different possibilities

Make a note of the base lengths of your triangles.

Notice anything interesting? Convince yourself it always happens.

The red line is half the length of the blue line. Numbers and letters inside a triangle represent its area. What can you say about $A+B$?

For each triangle with base lengths as shown, write C in terms of D.

Look at the diagram below (which is not drawn to scale).

The areas of three of the
triangles are shown.

What is the area of the quadrilateral $APOQ$?