The sum of interior angles of a triangle is 180 degrees. If we’re trying to find the triangles last angle on the right, we will subtract 180-60-50 which equals 70. The angle missing on the right side is 70 degrees. There are opposite angles in this shape so the other angle beside a would also be 70 degrees. Now we only have a left and you do the same thing with the sum of interior angles with that triangle. So you do 180-70-65 and you’re left with 45. Therefore, a is 45 degrees.
