Answer:
Step-by-step explanation:
All triangles have 180 degrees. There are no exceptions to that rule. You find an exception, you are finding something that can never be.
Call the missing angle x
51 + 73 + x = 180 Add numbers on the left.
124 + x = 180 Subtract 124 from both sides.
124-124 +x = 180 -124 The 124s on the left cancel. The right = 56
x = 56
