the interior angles have to equal 180 and the exterior angles have to come to 360 degrees
so you already know 23 to find the one by the 106 degree you use the linear pair postulate ( angles on a straight line will equal 180) so 180-106 equals 74. Now you have 2 of the three interior angles. To find the third you take 180 - 74 - 23 which equals 83 then you can use the linear pair postulate again and take 180-83 to get your answer for x which equals 97
