Charts like this, each chart represents a corresponding number.

Look carefully. If the two graphs do not conflict, it should be the number represented by the graph.

If you touch it, subtract the number represented by the image inside from the number outside.

So □= 1 ○=2 △=5.

So the triangle and circle of the last figure are not in contact with each other, so they should be added up.

The answer is 7.

All of the above is my understanding.