Area between two overlapping triangles

Question

The shaded part for 1 single triangle is $4/9$ths of the total area of the triangle. If this was considered to be 4 units, then the unshaded $5/9$ths would be 5 units. Thus the total area of the whole figure is 14 units and so $4/14$ths or $2/7$ths are shaded.

I believe that's the right answer, but can someone tell me is there a more efficient or a method that utilises geometry?

Thanks

Answer 1

Here’s a quick visual way of thinking that I would expect a 10- or 11-year-old to be capable of.

No arithmetic beyond counting nor a single word nor any spare space is necessary. (I presume expect that students are permitted to draw on or annotate their examination papers.)

(Each dot represents what we would call a unit of area.)

Answer 2

Do not worry. This is without doubt the easiest and fastest approach to solve this question.

So I feel like there is some assumed knowledge that I'm omitting

Mathematics is full of known results and equations, but you can't have known results for literally everything! :)