In this tutorial, we learn how to find the interior and exterior angles of a triangle. I triangle has three angles and their measurement when added together will equal 180. For example, if one angle is 80 and another is 30, then start off saying the equation equals 180. Write in 80+30+X in front of the equals sign, then subtract the combined like terms from the 180. After this, you will have found the value of x, which will also be the measurement of the last angle. Make sure to write out the units after this, and then you will be finished with the angles!