Write an equation.
- There is a total of 360 degrees in a quadrilateral.
- There are two equal angles (H and I), which can be represented as "A". The two angles are 78 degrees, so A = 78.
- There is one angle (G) that is 124 degrees, and can be represented as G.
- The missing angle is J, which is what we will solve for.
- To find J, we will subtract the 3 given angles from 360.
J = 360 - 2A - 124
J = 360 - 2(78) - 124
J = 360 - 156 - 124
J = 204 - 124
J = 80
Therefore, Angle J is 80 degrees.
Proof: 78 + 78 + 124 + 80 = 360.
