How do you know what angles they are talking about when they say some like ∠oca ∠cao ∠oab

The given angles are

When we write down angles, we have different notations to do it.

In this case, we have angles with three letter, each one indicates a specific element.

The first letter indicate the initial point where the angle starts, for example, , beginas at point B, the middle letter indicates the vertex where the angle is at, so indicates is at vertex O, at last, the third letter A indicates the final point where the angle goes.

Having said that, is the opening from point B, then goes to vertex O and finally goes to point A, in the image attached you can see this angle highlighted.

Using the same reasoning, we have that starts at points A, goes to vertex O, and ends at point C. Refer to the image attached.

c.35

step-by-step explanation:

8+13=21

21+8=29

29+6=35