The angles of a triangle always add up to 180°. This means that (x+46) + 52 + 92 = 180.
First, subtract 92 from both sides of the equation to get (x+46) +52 = 88. Then, subtract 52 from both sides of the equation to get x + 46 = 36. Finally, subtract 46 from both sides of the equation to get x = -10
