Respuesta :

∠ADC = 112°
∠ADC =6x + 7 + 12x - 3

Equate both:
6x + 7 + 12x - 3 = 112

Solve for x :
6x + 7 + 12x - 3 = 112

Combine like terms:
18x + 4= 112

Take away 4 from both sides:
18x = 108

Divide both sides by 18:
x = 6

Find ∠ADB:
6x + 7 = 6(6) + 7 = 43


Answer: ∠ADB = 43°

Supernova
If m∠ABC = 112°, then m∠ADB + m∠BDC must equal 112°.

Make m∠ADB + m∠BDC = 112.

6x + 7 + 12x - 3 = 112
18x + 4 = 112
18x = 108
x = 6

Now plug x into 6x + 7 to find m∠ADB.

6(6) + 7 = 43

m∠ADB = 43°