To find this you first find the angle opposite to 126. To do this you subtract 126 from 180 as 180 degrees is a straight line, and we are looking for that missing angle.
This equals 54 degrees.
Now, 54 + 43 equals 97.
Because all interior angles of a triangle always equal 180, you can find that last angle by subtracting 97 from 180. This leaves you with 83 degrees.
