we have,
angle ADB = 6x+7
angle CDB = 12x-3
angle ADC = 112°
but angle ADC = angle ADB + angle CDB
=> angle ADB + angle CDB = 112°
=> 6x + 7 + 12x - 3 = 112°
=> 18x = 112 - 4
=> x = 108/18
=> x = 6
angle ADB = 6x+7
= 6×6+7
= 36+7
= 43°
hence the measure of angle ADB is 43°