As we know, any straight line would have an angle of 180°. Also, when we see the right angle symbol (the box in the top left quadrant of the graph), that means the angle is exactly 90°. We are also given an angle of 47°. We can now set up an equation with the numbers we have.
90° + 47° + x = 180°
This basically says that all three of the angles we listed make up that straight line which would equal 180°. Let's work this down to our answer:
137° + x = 180°.........................................Add 90° & 47°
x = 43°.....................................................Subtract 137° from both sides
