Remark
All triangles have 180o. There are no exceptions to this statement.
Let the unknown angle = x
43 + 79 + x = 180
122 + x = 180 Subtract 122 from both sides
x = 180 - 122
x = 58 <<<< answer
The next problem should be a triangle. Look at the base which is a triangle. Any horizontal plane will cut out a similar triangle to the base.
