What is the measure of ∠j in this quadrilateral?

The two rings on angle I and H mean they are the same. You add those three angles together (280) then subtract it from 360 if it has four angles.
The answer is 80.

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.