Question

Here is a nice and not very difficult problem.

Answer 1

or

Answer 2

the answer could be 30 + 30 +30 + 40 = 130

Answer 3

It is right. Can you explain so people can see how you did it?

Answer 4

the outer triangles base was decreased by half and the height was increased by half.
so area would be 40*(1/2)*(1+1/2) = 30
rest is addition.

Answer 5

Thanks @expermentX

Answer 6

thank you too for problem.

Answer 7

Here are the details of the proof.