m∠ADC=m∠ADB + m∠BDC
134°=5x+4 + 7x-2
134°= 12x+2
-2 -2
132°=12x
/12 /12
11°=x
m∠BDC = 7x-2 = 7(11) -2 = 77-2 = 75°
m∠BDC = 75°
