Hi! So, here’s what I know. Every triangle will equal to 180*. So to check if that triangles is 180 we add all angles and it should add up to 180*.
Now the question is, Why it shows that the angles of a triangle equal to 180* when added up?
Note that we see all angles lie on a straight line, therefore we know that when we add angles that lie on a straight line it will equal to 180*, they will also meet at the same point.
This is all I can help with. Hope it helped something!!! Have a great day!