According to the meaning of the question, the lines inside the triangle are the three middle lines of the triangle.

According to the midline theorem, each midline is equal to half of the corresponding base.

The three sides of a small triangle are half of that of a big triangle, so its area is 1/4 of that of a big triangle.

So the areas of these four small triangles are all 1/4 of the big triangle, so the areas are equal.