Can someone explain to me how to solve this?

Question

anonymous · Answer

http://media.education2020.com/evresources/2090078_5y3x.jpg

mathstudent55 · Answer

You are dealing with a 4-sided polygon, a quadrilateral.
Do you know the formula for the sum of the measures of the interior angles of a polygon?

anonymous · Answer

There's a formula for it? o: Shoulda figured. What's the formula?

mathstudent55 · Answer

The formula is:
S = 180(n - 2)
where S = sum of the measures of the interior angles of a convex polygon
n = number of sides.

mathstudent55 · Answer

Since you have a quadrilateral, the number of sides is 4, so use n = 4 in the formula.
What do you get for the sum of the measures of the angles?

anonymous · Answer

S = 360?

mathstudent55 · Answer

Correct.
Now, before we use this info, let's look at something else.
Do you notice the red arrowheads on the top and bottom sides?
Do you know what they mean?