If you're being asked what rules/steps go in the blanks for the proof: Blank 1) Adding adjacent angles I'm guessing 54° is the angle measurement of ∠ADC. You know the measurements of ∠ADB = (3x-2)° and ∠BDC = (4x)°. Since those two angles are adjacent angles, meaning they share the same side B and the same endpoint D, they can be added together to create a larger angle, ∠ADC, that is the sum of both their angles.
Blank 2) Isolating the variable You are adding 2 to both sides of the equation to isolate the 7x.
Blank 3) Solving for x You are dividing both sides by 7 to get the value of x.
